Vikunja is one option. Selfhosted, open source and Trello-like.

Nope, not just you. Downloaded it and tried to start it, but kept crashing on me immediately every time. Switched to another app.

Using Connect because Jerboa just kept crashing on me at startup. Never got to test it out. Problems do exist in Connect, as e.g. I could not comment on this post in the app. Will check out Thunder and Lift off as well, so thanks for the suggestions!

Edit: I literally just found out that you have to hit the huge plus-button at the bottom right to add a comment… I always thought it was for creating a new post 🤦‍♂️