- Edited
@N1b this is what I ended up doing after trying all the different calendars including proton with a premium plan. It seemed very intimidating at first but was ultimately not a big deal in the end. Now I use nextcloud for everything (contacts, calendar, photos, cloud storage, etc)
There are privacy focused cloud servers you can use but I just bought a $50 mini PC off eBay and it's been working flawlessly.