There is a setting now (in all types of client I think) to log out when you close down the browser. Your comment makes me realize that I probably want to NOT set that on at least one machine. I set that on the machines that are out and about.

For the server I’ve used gogs for many years. It was easy to set up and has a web interface. What client you use is really up to you with git.

https://gogs.io/

you mentioned you’ve used joplin. All my notes are in markdown and I’ve been using Obsidian instead. Obsidian includes support for mermaid and can render (relatively simple) flowcharts.

https://obsidian.md/ https://mermaid.js.org/syntax/flowchart.html