You can tell git to use a specific key for each repo. I have the same situation as you and this is how I handle it.

https://superuser.com/questions/232373/how-to-tell-git-which-private-key-to-use

Docker, using the nextcloud:stable image (not-all in-one) with postgres, behind nginx, and finally ZFS with 2x modern HDDs for storage. I run the stock apps plus a small handful, and have carried the same database through many versions over the last 5 years.

It’s usable, but definitely not snappy.

The web interface for files is fine. Not instantaneous at all but not a huge problem. I have about 1TB of files (images and videos) in one folder, then varying files everywhere else. I suspect that the number of files (but probably not the size) is causing the slowdown.

Switching to, for example, the notes app is incredibly slow, and the NC Android app is just as bad.