Launching the program manually after each reboot is a hurdle, and has to be done via console with the Fedora repo build. This leaves behind its console window (as a novice user I haven’t ever really read the output).
Is it possible to create a startup entry in /home/user/.config/autostart and ensure that no console or any other window is launched in Gnome?
You need to write a startup script and use systemd to make it a service that starts up on boot.
I will paste two links that explain it. Let us know if you need further assistance!
NB: I am zero familiar with Syncthing, just wondering if it doesn’t provide a service that you can start/enable with something like systemctl start syncthing.service?