[caspar]

Been using syncthing with keepass(X/XC) for probably half a decade now and it works great, especially since KeepassXC has a great built-in merge feature for the rare cases that you get conflicts from modifying your vault on different clients before they sync.

The only major point of friction with syncthing is that you should designate one almost-always-on device as "introducer" for every single one of your devices, so that it will tell all your devices whenever it learns about a new device. Otherwise whenever you gain a device (or reinstall etc) then you have to go to N devices to add your new device there.

Oh, and you can't use syncthing to replicate things between two dirs on the same computer - which isn't a big deal for the keepass usecase and arguably is more of a rsync+cron task anyway but good to be aware of.