Does anyone know why there’s no desire to see a working standard (protocol) for calendar/tasks?
It’s clear that CalDAV doesn’t function consistently across devices (and does seem to be dying as a standard). If you work across different devices/OS it’s virtually impossible to get things set up seamlessly. Companies and developers of task apps seem happy to create silos and not look at interoperability.
If you want to self-host, it’s too hard to do this and you really are limited to a tiny number of options.
Nextcloud as the server and DAVx⁵ with Fossify Calendar as the client on my phone. On my laptop Kontact, but I haven’t looked at that in ages, so it could be in shambles for all I know. I think I’ve also used Thunderbird with some plugin.
And my Fritzbox router uses CardDAV to populate the phonebook of all connected phones.