Log for firewall offered by your VPS host / service provider? I don’t know…
Let’s try something wild that may get you access to Virtualmin even if port 10000 in not open in the VPS host / service provider firewall! This method is perfectly safe and easily reversible if it does not work. In Virtualmin -> antoniodellalibera.it (or any other domain) -> Server Configuration -> Edit Proxy Website, in the " Proxy to URL" field, enter https://80.88.91.147:10000/ and set “Proxying enabled?” to yes. Click “Save and Apply”.
Then open https://www.antoniodellalibera.it/ in the browser. If everything works as I expect, you should see the Virtualmin GUI / login screen instead of the normal website associated with the domain.
I shall await your feedback.