Does anyone have recommendations for a good file syncing app?

Currently I use Synology Drive Sync, which works great. I have Drive Server running on my NAS, and Drive Client running on my PC. But I've been slowly moving away from bare metal applications, just in case I switch off of Synology one day.

I'm looking for something well polished that has versioning, as well as file manager integration with Windows Explorer (so it shows check marks on files that are sync'd).