Nothing. restic mount must continue to run in order to serve the contents of that directory.
If you want to run it in the background, you could use:
nohup restic mount >restic-mount.log 2>&1
Though this will not work unless you supply the password using --password-file, --password-command, or the RESTIC_PASSWORD environment variable since it won’t be attached to the terminal to be able to ask for the password interactively.
If you intend this to run all the time as a service, it may be better to create a systemd unit for it.
Note that if you may need to run with --allow-other if you are sharing the mountpoint with Samba, unless smbd is running as the same user (unlikely).
Thanks for the tip!
Since I’m calling if from a script another & at the end of the command was needed.
Everything runs now as expected: unmount, backup, mount, script exit + mount continues