I ended up on Piwigo. It’s pretty fully featured and allows you to set up access controls for groups. Also has client apps.

Lol… Well I’m glad someone saw it :D

These are fully stand alone. Downloadable. So not strictly hosted I guess?

Does it need to be “hosted”?

I like both these:

yEd (https://www.yworks.com/products/yed)

Dia Diagrams (http://dia-installer.de)

I think yEd had a free version but closed source.

You might find some starting points or even projects or terms to look for in this article:

https://arstechnica.com/information-technology/2023/03/you-can-now-run-a-gpt-3-level-ai-model-on-your-laptop-phone-and-raspberry-pi/ .