Do you have an idea? Whether AlternativeTo nor OpenSourceAlternativeTo got an answer.
EDIT: I should have had added, that I was not looking for the financial aspects of the app, but I was looking for a possibility to store tickets and cards: Catima offers at least somewhat, what I was looking for.
A shame that this search turned out null, but at least I learned about https://www.opensourcealternative.to/