SyncThing, being solid and open source (and not beholden to commercial interests) would be my suggestion.
I just installed the DB client on a new Mac and it is very aggressive about trying to trick me into enabling Accessibility access (i.e. full control of the machine) and ghost files (ones that get faulted in when you read them) -- which I'd enable if they could still be indexed by Spotlight, a feature the old Sherlock had.
Dropbox used to surreptitiously stick itself on that list without asking, but Apple forced them to request explicitly. I think that was underhanded of DB and I don’t trust them.
Does anyone know of a more accessible way that could solve this?
The same service is also available trough Cyberduck and Mountain Duck (https://cyberduck.io/cryptomator/).