Time to throw my two cents into this I guess.

It's interesting that people continue to use the "steeped in twilight" as evidence despite the fact that they're willing to turn the other cheek in the face of the Koroks and Rito on grounds that they can exist in the other timelines too. By that logic the line given shouldn't really be indicative proof that it's in the Child Timeline
The difference is that knowledge of the events of
Twilight Princess is confined to the Child Timeline, while the Koroks and Rito could exist in any timeline. In fact, we already know that the Rito exist in the Child Timeline based on the retconned mural in
Twilight Princess HD, and we know from Aonuma's interview that the Koroks in
Breath of the Wild are unrelated to the ones seen in
The Wind Waker.
more like a reference (like Wind Waker talking about a fairy boy who made maps for the Hero of Time, alluding to Tingle in Majora's Mask, or the sword Phantom Ganon inscribed with the blacksmith's name from the very same game.)
When we selectively pick what's a reference/easter egg and what's evidence, we get nowhere.
First, I'd like to know what you're specifically talking about with regard to the Tingle reference. I'm unaware of any lore-based evidence for knowledge of the events of
Majora's Mask in
The Wind Waker.
With regard to Phantom Ganon's sword, that could be an easter egg, or it could be that the sword was crafted by Zubora and Gabora, their never-seen Hyrulean counterparts, or characters in a more recent era by the same names (e.g. Beedle's apperances). Either way, it's easily explained away. A direct reference in a pivotal cutscene to
Skyward Sword,
Ocarina of Time, and
Twilight Princess as the explicit history of the Master Sword is exactly what one would expect to be considered the history of the Master Sword in the Child Timeline, and there's no lore-based reason I can come up with for people in the Adult Timeline and/or Downfall Timeline to be aware of the events of
Twilight Princess.
I also don't consider the DLC to be canonical evidence either, considering that by that point we may as well throw in amiibos and, well, that just muddies the waters too much.
I've never considered the amiibos canon, and I no longer consider the DLC armor to be canon.
I'm rather partial to BotW's placement being in the Fallen Hero Timeline, mainly because of two large pieces of evidence:
- Calamity Ganon himself. The fact that he is referred to as Ganon in this timeline whereas he's usually known in the other two by the moniker of Ganondorf. That's not to say he couldn't be known as such in the other timelines but already the Fallen Timeline has the most "Ganon" appearances out of the three. As for CG's Ganondorf-like traits, I don't really see that as being indicative of timeline placement since Ganondorf himself canonically predates the timeline split, so it really gets us nowhere.
First, Ganon has existed in all three timelines, so the moniker of Calamity Ganon is not evidence of timeline placement. We also know that, for unknown reasons, he's taken on the form of Calamity Ganon, which is different from any previous Ganon(dorf) incarnation in previous games.
Second, as a side note, it should be noted that the quadrupedal Dark Beast Ganon has only appeared twice: in
Twilight Princess and in
Breath of the Wild.
Third, all traces of the humanoid Ganondorf were erased in the Downfall Timeline during the events of
Oracle of Seasons and
Oracle of Ages, leaving only a "mindless beast," which is why Calamity Ganon's cunning and partially-regenerated humanoid appearance in
Breath of the Wild contradicts the Downfall Timeline.
The Triforce. In both the Child Timeline and the Adult Timeline, the Triforce is normally split into its three main parts and exist inside Zelda, Ganondorf and Link. The Fallen Timeline differs from this as the Triforce is either held entirely by one person or just sitting around in its completeness, the main exception being A Link Between Worlds where they follow the "held by Zelda and Ganon" except that the Sages have the Triforce of Courage. BotW Zelda is seen possessing the entire Triforce inside of her when using her sealing magic, which again alludes to the Fallen Timeline.
There is no reason to think that Zelda possesses the full Triforce in
Breath of the Wild. Her sealing magic is the result of her bloodline, due to the fact that she's descended from an incarnation of the Goddess Hylia. The Triforce symbol here is symbolic. If she possessed the full Triforce, she could single-handedly wish away Calamity Ganon. The state of the Triforce in
Breath of the Wild is unknown, although the new
Master Works book apparently makes mention of it. I'm waiting for the translations to start appearing online. I've got my own headcanon about the state of the Triforce in
Breath of the Wild as it relates to the Child Timeline, but it's not supported by evidence, so I'm not going to mention it here.
The Twilight Princess location evidence is interesting in that since the game is basically a giant love-letter to Ocarina of Time as evidenced by it being the same looking Hyrule, we have to consider that some of the designs seen in Twilight Princess also may be true of OOT, which again predates the timeline split.
A lot of the location evidence that connects
Breath of the Wild and
Twilight Princess does not predate the timeline split. I'm going to quote a post I made earlier about why the Child Timeline is the most likely timeline placement for
Breath of the Wild, and then I'm going to address it in the context of translated evidence we've already gotten from
Master Works.
While far from definitive, here are the top reasons to think
Breath of the Wild takes place in the Child Timeline:
- Princess Zelda mentions, in order, Skyward Sword, Ocarina of Time, and Twilight Princess as the history of the Master Sword. There are variations in the different localizations regarding the off-screen audio only, but the opening part of the speech, with text, is consistent across localizations. In the English localization of off-screen audio, for example, the alleged reference to A Link to the Past and The Wind Waker goes something like "across the seas of space and time," which isn't actually a direct reference to anything.
In the summer DLC pack, it includes an in-game story about the thief Misko explicitly stealing, among other things, a replica of the helmet Midna wore that the royal family gathered in an attempt to collect artifacts significant to the history of Hyrule. The canonicity of the DLC pack is questionable, but if this isn't canon, neither is the in-game story content of the winter DLC pack. Moot when you consider the new DLC pack.
- As of Ocarina of Time, the Gorons lived on Death Mountain, and the Zora lived in Zora's Domain. In the Adult Timeline, Hyrule is flooded. The Gorons become traveling merchants, and the Zora evolve into the Rito. In the Fallen Hero Timeline, the Gorons and the Zora are displaced from Hyrule entirely, if not killed off. In Breath of the Wild, the Zora still live in Zora's Domain, and the Gorons still live at Death Mountain. It's possible they could have returned later in the Fallen Timeline, but that requires a lot of mental gymnastics, and the simplest option is Breath of the Wild takes place in the Child Timeline.
- The Gorons have various Gorons important to Goron history carved into a Death Mountain rock face. One is Darunia from Ocarina of Time, and one is Gor Coron from Twilight Princess.
- There appear to be various landmarks from Twilight Princess present in Breath of the Wild. To name a few, Hyrule Castle is clearly the design from Twilight Princess, the Goron Mines from Twilight Princess are present, and the Great Bridge of Hylia from Twilight Princess is present.
I'm not aware of any real reason to think
Breath of the Wild takes place in the Fallen Hero Timeline, and the only real reason I can think of to think it might take place in the Adult Timeline is the presence of the Rito and the Koroks.
In a nutshell, if we're trying to figure out which timeline placement is most likely while making the fewest assumptions possible, a Child Timeline placement is clearly the winner. However, there's evidence for and against all three timelines. Regarding the Child Timeline hypothesis, the thing that seems to contradict it is the Zora tablet:
"Long, long ago... In a past more distant that even the Great Calamity or the creation of the Divine Beast Vah Ruta... There was a Zora princess named Ruto. We know that she was an attendant to the Zora patron deity and that she was a fair and lively girl, beloved to all. Around that same time, an evil man with designs on ruling the world appeared, bringing disaster upon Zora's Domain. It is said that Ruto then awoke as a sage, facing this foe alongside the princess of Hyrule and the hero of legend. Her achievements are remembered not only by the Zora, they are also forever etched into the history of Hyrule. The Divine Beast Vah Ruta, built ages later to face off against Calamity Ganon, was named in honor of Ruto. That the Zora princess—my sweet daughter Mipha—was chosen to pilot Ruta is surely the work of fate."
Regarding a Downfall Timeline or Adult Timeline hypothesis, the thing that seems to contradict it, among other things, is the ceremony speech:
"Whether skyward bound, adrift in time, or steeped in the glowing embers of twilight… The sacred blade is forever bound to the soul of the Hero."
This leaves us with two options:
- It's the Child Timeline, and they have some knowledge of the Adult or Downfall Timeline.
- It's the Adult or Downfall Timeline, but they have some knowledge of the Child Timeline.
If we consider that the Hero of Time, with knowledge of the sage events of the Adult Timeline, time-traveled back in time to the Child Timeline and recounted the events to the Royal Family, Option #1 is plausible. This is the point when a fan of the Downfall Timeline argues that the tablet doesn't mention anything about alternate timelines, or he or she argues that this is a bit of a stretch, but given the following from Master Works, this explanation is the only one that makes sense if we assume
Breath of the Wild has to take place in one of the three canon timelines:
"The kingdom of Hyrule has a long and storied past, where the events of one era may just be ancient myths in another. Since olden times, the land has repeatedly undergone periods of prosperity and decline, so much so that it is unknown whether the legends passed down are actually true, or simply fairy tales."
This blurring of history and myth has created legend, which is all the Zora tablet is. Once you've explained away the Zora tablet, there's every reason to believe
Breath of the Wild takes place in the Child Timeline, and there's no real reason to think it takes place in the Downfall or Adult Timelines.