I use Syncthing and KDE Connect both. They're fantastic at what they do- wireless sync specific folders between devices, send/receive files, share a clipboard between devices, remotely operate a device, share notifications etc. Basically you can create your own seamless ecosystem of devices that belong to any platform! If you're like me and use a lot of offline-only apps, these two will let you sync your data between 2 or more devices. I use it for my offline music library (fully legal of course, no question about it haha lol), logseq notes, books (again, definitely completely legal).

I also use BitWarden, but I might switch to Keypass because it is fully offline.