I use a self-hosting Baïkal CalDAV server with Tasks.org (https://f-droid.org/en/packages/org.tasks/ https://f-droid.org/en/packages/org.tasks/ ). The advantage

I use a self-hosting Baïkal CalDAV server with Tasks.org (https://f-droid.org/en/packages/org.tasks/ https://f-droid.org/en/packages/org.tasks/ ). The advantage of this is that it works with email clients.