Proton cal

Yes, please, following for recommendations 🙏🏼

https://zapstore.dev/apps/naddr1qqgxxmmd9ehx7um5wf3kzmpwv9c8qq3qpatrlck0muvqevgytp4etpen0xsvrlw0hscp4qxgy40n852lqwwsxpqqqplqkjhc7d2

https://zapstore.dev/apps/naddr1qq8kxmmd9ecxcettw3hhxtnpwpcqygplwuxkt5a8vj5utj6s8tsj8e3wcavc45p4mqmw92qs7wrh5azmyspsgqqq0c9savs8q5

Tuta cal

Well, that depends on whether you want to host it, or let someone else do it for you. People already suggested Tuta and Proton. Both are hosted and supposedly encrypted. The UX varies, and is a matter of personal taste. You could spin up a very light version of Nextcloud in order to use their cale...

davx (caldav) with https://github.com/FossifyOrg/Calendar

Gm

Most of apps are like that one and don't even warn users about the risk, unfortunately.

Just because many recommend Tuta: Tuta is garbage. Stay away. They have not been able to implement easy to ad features for over 2 years. Doesn't surprise when you look at their 'woke level'. They probably have other priorities. Go with Proton or self hosted Nextcloud.

Fossify calendar (+ DAVx5 if needed)