Connections timing out have always been a firewall issue for me.
Client sends packet, firewall drops packet, client waits for a reply that’ll never come. Client times out.
I would check firewall logs or temporarily disable it to see if it works without it.
so yeah check the firewall on the server, the client and in between ( if any ). That’s what I would do.
Maybe one of these is interesting? I have no actual experience with them though:
https://github.com/DumbWareio/DumbBudget
They should all be self-hostable.
Edit: I don’t know of these all match your criteria. Maybe finance looks pretty Sleek imho. I just dread the thought of exporting my transactions and importing them because my bank is forking horrible w.r.t. integrations.
And logging in every time to do a CSV export is just annoying.
Edit 2: formatting
What game is this even from.?
Worth every goddamn cent I paid for it.