Personally I was delighted to discover
https://circuit-board.de/forum/index.php/Thread/13913-STRIP-CLUB-PCB-Scans/?pageNo=1
some months back and pushed things forward considerably over what was otherwise known before.
If you are coming to us more from things with chip recreations, actual service manuals, recreated, leaked or straight released then... yeah. The gigaleak stuff had some CAD files for some things but nothing of particular note here that I have seen, though I don't know people would have looked at it or considered it as much.
To that end I have nothing you could not get searching on the likes of
https://octopart.com/ ,
https://www.findchips.com/ or the usual suspects for chip vendors or whatever the part vendors themselves have (or have in a similar series if doing custom chip but basically different pins and some different tolerances to make it cheaper).
If you had seen that thread before then if there was any discussion from the groups doing various DAC replacements, amps and whatnot on what could be relevant here. However even those are usually more for the "these resistors limit volume because French regs/EU regs/common sense says/my particularly forward thinking injury lawyer consultant says for earbuds, replace with lower resistance to blow those eardrums faster", "here is the output according to my oscilloscope so tap this point for input in a further amp stage", "here they skimped on a capacitor in this version/revision* and used a noisy line, they even left a nice pad unpopulated" rather than going for deep understanding a la some of the hifi stuff I have seen over the years or old school radio stuff. If there is a particularly notable failure case (see some of the gamegear and megadrive fixes and improvements) then that might get known as well.
*even a decent breakdown of differences between board revisions would be a gigantic leap. Can do OK for shell colours though --
https://gameboy.fandom.com/wiki/List_of_Game_Boy_System_Colors_and_Variations .
Can do you a very nice line in terms of internal hardware descriptions as understood by the software though
http://belogic.com/gba/ . That sort of thing is what most console homebrew scenes seem to focus on.
Even reading that referenced post I am not entirely sure what is going on with that one. Could be any number of things, meanings, wrong terms (derp moment or otherwise).