And it will autostart on startup. You might want to remove what insync puts in /etc/xdg/autostart or whatever it uses to autostart. I wish Insync adapted it itself, systemd is meant for this.
Yes, that is indeed better. I previously had oneshot where RemainAfterExit might have made sense, but I changed it to forking because it would not restart on failure, I just forgot to remove that line. I am changing it in the original post for people who do not read the comments, thanks for the suggestion!
Actually, now that I tried it, systemctl restart and systemctl start does not work without RemainAfterExit=yes. From what I can find, Insync is not forking itself properly, so systemd files to track it well. Systemd would like a PID file, but that is also not provided, as far as I can tell. But it seemed to me the restarting after a crash worked, I will keep an eye on it.