Fixed it by manually updating windows 10 to the 20H2 version. Google windows update assistant for more info.
After playing for the past couple of weeks without problems, today I cannot join my regular server. Sometimes the battleye service outright refuses to start, then when it does, the server I normally play on (an official 1pp server) boots me for battleye reasons. I sometimes get "lost connection to the host", "battleye error: please restart your game". At one point I got battleye "bad service version" message.
On top of that, suddenly the game needs 5 minutes to even start. I didn't change anything at all, but before I tried starting it up today I did get a message that something needed installation.
I tried a complete fresh install of the game, uninstalled and reinstalled battleye a couple of times, latest graphics drivers, the works. Nothing fixes it.
As you can imagine, this is really frustrating. DayZ is one of the only chill games I have left that I can play during the weekend, and now even this doesn't work anymore.