I followed this advice:
It might be installed but I have no icon in the apps menu.
When I use the command
systemctl status firstname.lastname@example.org
with my choice of username it says its inactive(dead).
Then below the Main PID bit where that link suggest two lines should follow, I get 10 lines with this kind of thing:
Failed with result ‘exit-code’.
Service hold-off time over, scheduling restart.
Start request repeated too quickly.
The last line being:
Failed to start Syncthing - Open Source Continuous File Synchronization for
I am giving up on it until you develop an easily downloadable GUI if nobody can help.