syncthing/etc/linux-systemd/user/syncthing.service

[Unit]
Description=Syncthing - Open Source Continuous File Synchronization
Documentation=https://github.com/syncthing/syncthing/wiki
After=network.target

[Service]
Environment=STNORESTART=yes
ExecStart=/usr/bin/syncthing -no-browser -logflags=0
Restart=on-failure
SuccessExitStatus=2 3 4
RestartForceExitStatus=3 4

[Install]
WantedBy=default.target