Hmm, Dokuwiki is a reallllllly underrated wiki software that is extremely lightweight and doesn’t require a database to run on (files are just stored in a folder). Multiple different wikis can be run on the same Dokuwiki server with plugins and in general it is a supremely easy way to host a body of text and images that can be easily edited by multiple people (or be kept private). The media manager for uploading images and managing them is really nice too.
Backing up your wiki on Dokuwiki is also absurdly easy because it is just a folder… that you can backup in any number of ways (git… syncthing… whatever).