+1 for Baikal. Also, radicale is very simple to host in docker. Thunderbird works great with calDAV and will give you desktop notifications, davx5 is a great bridge to get your CALDAV server into android calendars. Hope that helps!
Yes, frugal usenet. Buy a year for 40 or 50 bucks, get a free block. US servers, EU servers and a backup server too. All for less the 5 smackers a month.
Cheers mates, keep up the good fight. Much appreciated.