Normally you would have in each file a license header and depending on which license the file ia it would have a different header if the licenses are mixed.
Often we don’t copy the library source code into the same git repo but use some package manager which installs them for the user.
In that case if the whole git repo is the same license then often we just have a LICENSE file in the root which ia mentioned in the readme.
Back in the day we made https://github.com/Pelagicore/OpenSourceTemplates
It has links to SPDX descriptions ect which are best practices in this regard.
I’m already hosting something similar I think. I am hosting a Immich instance for me and my wife to back up our photos from phones and computers and I also host a PeerTube instance for videos and some audio (I don’t have so much audio only).
What would make me trust a special software for it is things which validate it from outside like stars on github or other people blogging about it what they’re using it, and history which is at least a year so I can see that it’s not just a quickly vibecoded project which will be abandoned soon. Also if there would be a export to HTML or so so that I could get a static archive if the project really stops being supported.