I also wanted to avoid Google calendar and ended up with this setup: I have a little linux server home with Nextcloud running on it, where caldav and carddav can be used. In order to sync the outlook calendar at work with the home server, I installed a sync tool to work PC: https://caldavsynchronizer.org/.

With this setup, I can sync my calendars and contacts between personal devices and work pc. With iphone, one can use cal and carddav out of the box. I remember using https://www.davx5.com/ on my android phone last year. I am not sure if it would still be necessary though.