FirewallD error

Good morning,
I wanted to ask how come when I modify, on debian 10 server, deleting mail services the FirewallD after asking to apply the changes gives me this result: Failed to list zones : Error: INVALID_ZONE, with debian 9 everything ok instead?
Thank you for your attention, my best regards.

This is strange. If the public zone were actually missing you’d have bigger problems than that error. Do these commands report anything useful?

firewall-cmd --get-zones
firewall-cmd --get-active-zones

There’s a lot of info about the error if you search it. The OS shouldn’t make any difference.

Blank XML zone templates are stored in /usr/lib/firewalld/zones if you decide to replace a zone in /etc/firewalld/zones for a clean start.

If it seems hopeless you can always remove and reinstall Firewalld. If you reinstall it from Webmin instead of the command line you’ll have the benefit of a fresh public zone with all hosting services/ports opened and ready.