**** Check to see if VIrtualmin presently supports the version of the OS you want to upgrade to as without this step it’s possible that even on a fresh install things won’t work if major OS and software changes are not understood by the “min” software. ****
== OPTION #1 ==
Make a backup of your hosted files, and perhaps a backup of Webmin itself.
Proceed if there is a “safe enough” way to upgrade between major versions.
Test to make sure things still work as intended.
== OPTION #2 ==
Install new OS version on a fresh system.
Install Virtualmin and configure
Migrate websites from old server to new server
*** Migration can take on multiple forms, either using the “min” built-in backup/restore functionality (or similar features) or my preferred way which is old school where you create accounts, and migrate the data manually ***
There are pros/cons to either option above, but again make sure the OS and version you are moving towards is actually supported by the “min” software.