Some things (not exhaustive) I'm thinking of that would be useful:
- Manuals, schematics
- Part numbers for replacement parts (and where to get them, or what their equivalent part numbers from other brands are, etc.)
- Internal tools for flashing new firmware or unbricking devices
- Historical firmwares
- EOL information
@joepie91 I know some wikis like wikichip and there seem to be websites like https://repair.wiki/w/Repair_Wiki but I don't know how widely used or exhaustive those are, usually these things are very spread out, centralizing them is hard (also because those individual sites get updated sometimes), and then there's some OEMs that may object to schematics and such being published, so for those you have to look in good old torrents and such (try macbooks for example, lots of torrents for the schematics of it)
(I am aware of iFixit, but aside from that being a company, it is also much more limited in scope - as far as I can tell, it only really covers repairs of hardware for its original purpose.)