Really? I've had no problems with his recent 3DS CFW installation and system transfer videos.
This particular video is, like
@Kwyjor stated, bad – which I can say after watching less than 30 seconds on the end part. Granted, the tedious task of unwrapping multiple games after running Faketik instead of using Cthulhu to unwrap all software is a minor annoyance.
Restoring the NAND without even mentioning¹ possible problems when using the source system online if a big "no-no".
I've seen one video by this guy where he repeatedly said: "
Then select bla. Then select blubb, Then select ble. Then select…" That is – in my opinion – not how to make a good tutorial.
Videos can get outdated in no time: The last 3DS update fixed the browser holes and all the mass of "Super Easy 3DS hacking (2021, 11.14 firmware) " videos became useless in a second, requiring the video authors to create new videos for Seedminer or reactivate and update older videos. Until YouTube search outputs the new videos there is a lot of potential for confusion if older videos aren't removed. The Guide was back to Seedminer almost instantly (since all that had to be done was adjust some links).
There is a another problem with the video guides; and it is my personal main reason to advise against video guides in general: Regular helpers in the 3DS section of GBAtemp are used to 3ds.hacks.guide. We know The Guide. We know it is good, correct and tested. If something goes wrong or somebody doesn't know what to do at some point, it is easier for us to help.
Whenever somebody comes with: "I followed this video [embedded YouTube window] and now…" I feel like screaming: "Noooo. I don't want to watch half an hour of video just to see if the video is acceptable and what could possibly be problematic, incomplete or have potential for misunderstandings".
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To give another answer the initial question of this thread… We have a good and short tutorial for this topic:
https://gbatemp.net/threads/how-to-...-without-losing-non-legitimate-titles.531950/
There is no NAND restore in there, and this is good. The official transfer also includes the Activity Log, the save data of preinstalled titles, step history…
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¹ I didn't watch the beginning if he does say some warning it at any point. In any case: A warning belongs exactly at the point where he restores the NAND and there is none.