I think this probably still won’t do what you want, but actual-helpers has a script that will track the balance of an investment account. It won’t track shares or funds separately or anything, but it could maybe be enough if your goal is just net worth tracking?

Another vote for actual. It’s my first budgeting app so I don’t have anything to compare it to, but it was super simple to set up (as far as self hosted apps go), I really like the web ui, and simplefin works to sync with all of my banks/accounts. My only gripe with it so far is that it could probably use a better mobile experience.

This doesn’t exactly answer your question, but I use the binhex qbittorrent-vpn image for this. It might work for you too unless you were wanting to be able to reuse the same wireguard container for something else?