This is a simple guide on how to synchronise contacts and calendars between a desktop operating system (Windows, macOS, Linux) and Android relying on a combination of Syncthing and Radicale. The main goal and idea is to have Radicale running on every system locally, so that you can connect with it even when there is no network connection available. This applies to both desktop operating systems and Android as well. Desktop: Install and run Radicale following instructions from https://radical...
I agree, the described system seem unnecessarily complicated. Decsync exists exactly for that use case.
Here is the bug btw in case someone is interested: https://github.com/39aldo39/Radicale-DecSync/issues/33