oki, I found the problem is in launchd: it doesn’t inherit environment variable, so no $HOME was set and restic complained about not finding the cache. After adding to the plist the following it’s working as expected:
<key>EnvironmentVariables</key>
<dict>
<key>HOME</key>
<string>/var/root</string>
</dict>
Indeed Example: Scheduling regular backups on macOS states:
Use .bashrc or .bash_profile to export any environment variables your restic command may need, for example, the repository password. (This is convenient because it also allows you to get them in any Terminal you start.)
But I thought it was related only to specific restic env variables don’t I didn’t need since I pass everything as command params
I’m sorry I pointed out the problem for restic while it was my setup (and my scarce knowledge of launchd ;))