I dreamed of this for a long time.
Being always on the road, I often have my emails/contacts/todolist/pictures/whatever scatered accross all my devices, with no easy way to synchronize them without getting access to wifi.
This means in transport, in the country side, or in another country, my system is in shamble. Also, it means everything is slow to sync.
Yesterday I had to send a AI model to my colleague next to me. I was on linux, he was on windows. The fastest way was to get a usb stick. That should be a click in 2022. The closest to something reliable to do this was duckto, but it's not maintained anymore.
Good luck to ditto!
Syncthing is painless, with available local network detection of other clients. If either device has a webcam, the QR codes in the web UI make it quite quick to have a synchronized folder between two systems.