Ask HN: Shared Calendar Recommendations

Family life is slowly starting to make my planning efforts more complicated especially now as kid is growing up and we both juggle multiple hats. As a result, what I think I want to do is have a shared calendar for my family, but with the following restrictions:

- not bound to google/apple ecosystem ( I can move it around as needed ) - can be self-hosted

PS. I am not asking this question, because there are no options. The issue is there are too many and I just need something simple that will work on both android and apple ( and I don't want to keep testing 20+ projects ).