How to go about self hosting a wiki of repair guides?

Why not contributing the guides on ifixit and just keeping local copies? You can at least save a pdf copy?

How often will your internet go out? You could also cosnider an archiving solution for visited pages. Archivebox comes to mind.

Don't Louis Rossmann launched a repair wiki a while back?

Anyway, mediawiki wikis have a special page that lets you dump the wiki's contents for migration purposes, but I forgot whether it's locked to admins only.

Edit: here's a publicly accessible export page: https://repair.wiki/w/Special:Export

First ones that come to mind are:

https://www.bookstackapp.com/ - sets out your uploaded data like books. Can do books, chapters, pages, etc.

https://www.dokuwiki.org/DokuWiki - more standard wiki, also everything is stored in plain text so it's easy to distribute and use source control on (no database backend)

https://tiddlywiki.com/ - full fledged wiki, bit different layout though since it's all on one page. Clicking an internal link scrolls to that page so it's pretty quick.

All are free and open source, almost certain they all have docker images too. I haven't tried any of them but I've looked into them since I've been thinking about it

I recommend using Kiwix, https://kiwix.org/en/

They already have a monthly archive of ifixit available: https://library.kiwix.org/viewer#ifixit_en_all_2023-10/home/home

There are tons of other offline resources available for Kiwix as well https://library.kiwix.org/#lang=eng