Mailbox.org is great, I like that you get caldav and carddav as well. They’re very privacy conscious as well. It’s true the recent price increase doesn’t make me happy either. The service is great and I couldn’t find a better deal so I stick with them. Except for the price everything is perfect imho
I had radicale running for some years, it was finicky to set up I remember doing a fix in the code. But when it worked it did so without issues. Not sure how active development was in the last years maybe it has improved.