syncthing starts with a systemd service
now it logs to stdout
how can I tell it to log in /var/log, have a filesize max 50 MB and to have only 2 old files ?
Yeah, you can experiment with those, or alternatively, just do -logfile=default, which will rotate between 4 logfiles, each limited to 10 MBs. They will be saved in the Syncthing home folder.