

If you’re looking for a different approach, I moved from Nextcloud to Radicale for my family calendars, which includes ToDo functionality.
From an app point, for Android I’m using Fossify Calendar (which I think you’re using?) and Tasks.Org ToDo - and this definitely handles recurring tasks (inc. with different types of schedules)
From a remote access point of view, I have HA Proxy to convert the internal HTTP traffic into external HTTPS traffic (with Lets Encrypt certificate)
(Yes, I also have a VPN for other things… just focusing here for the calendar / todo)
We use VNC as we can record the sessions easily for later priof / discussion with our customers.
It’s in a VPN tunnel of course.
But of course, we also don’t use Google, AWS, etc as they’re not secure enough for us and we have our own SOCs