I found out that in webmin is used Linux IPtables
Using Ubuntu 20.04 2 the console commands to activated and configure IPtables are not visible in the webmin Linux IPtables interface (version 1.973)
The other things I found that refresh of webmin modules who are in the un-used part is working for one time.
The second time you perform this action this message will appear and will remain there for many hours
Checking for usable Webmin modules ..
.. found 59 with installed applications, 50 not installed.
I had to choose a other menu item to be able to continue
Greetings,
Gentle
Webmin by default only shows firewall rules that are saved in a config file - it won't show rules that you manually added with the
iptables
command.