I have an instance of Gitea that I use to mirror stuff.

Tailscale would allow you access to everything inside your network without having it publicly accessible. I highly recommend that since you are new to security.

I used to be a heavy GnuCash user, but when we got serious about getting a mobile app, I ended up trying YNAB.

It isn’t self hosted or open source, but we’ve more than made back the subscription price with money saved using their system.

It has a learning curve for sure, but the mobile app and transaction import has been worth it.