Rated 4 out of 5 stars
I suggest to point out in capital letters that CalDAV integration with Google calendar has some big issues since some days (very likely on Google side), and that a good and easy solution is to install and configure the Provider for Google Calendar Extension.
I was about to dismiss Lightning, after many years of contnuous usage, since I wasn't able to dismiss my alarms any more.
Now I'm very happy not to have to.
Note that the Google Calendar Server issue was fixed, it should now work without issues again.