FYI, if you are doing WebCal, CalDAV, and CardDAV sync on Android, the DAVx5 and ICSx5 apps are paid on the Android app store. But free with a donation link on F-Droid. I wish I had known this when I went down this rabbit hole a few weeks back.
Anything that gives Google less money and more to the developers of apps that don't suck is a win in my book.