I've not yet given it a go, but been meaning to try Ghostfolio

@OpenAltFinder I'm using Portfolio Performance, which is a Java desktop application based on Eclipse.
https://www.portfolio-performance.info/en/

A friend of mine is building something like that but it's still very early days, also I think it's limited to eToro I think. Usually APIs are available so maybe there's a possibility to whip something up yourself

The problem is access to market data. You are not going to find reliable (free) APIs for all the shares you want, never mind mutual funds etc.

If anyone knows options for UK/US data that is likely to remain free for year then let me know!

You can just scrape brokers websites of course, but it gets funky when there are splits/reverse splits/mergers.

If it's specifically portfolio/investments you're after, Ghostfolio is the popular self-hosted pick and it's good.

Mine's another option (disclosure: I'm the dev), Finlynq, AGPL, docker + postgres. It does lot-level cost basis, realized gains by tax year, dividends, and multi-currency with historical FX. Bonus: built-in MCP server so you can ask an AI assistant about the portfolio directly. Self-host or hosted.

Vs ghostfolio it's broader (full budgeting/accounts too, not just investments) but younger. Actively developed, so if there's a portfolio feature or broker import you'd need, I can bump it. Repo: github.com/finlynq/finlynq

It's been a while since I used it, but I think kmymoney has some basic features in that direction.