I'm working on a caldav compatibility checker side project. While doing so, I'm working on redefining the "compatibility matrix". This should only affect the test code. If you maintain a file tests/conf_private.py, chances are that the latest changesets will break Since "running tests towards private CalDAV servers" is not considered to be part of the public API, I deem this to be allowed without bumping the major version number. If you are affected and can't figure out of it, reach out by email, GitHub issue or GitHub discussions. (Frankly, I'm interessted if anyone except me uses this, so feel free to reach out also if you can figure out of it).
As always, the new release comes with quite some bugfixes, compatibility fixes and workarounds improving the support for various calendar servers observed in the wild.