Trying update get this error

SYSTEM INFORMATION
OS type and version Ubuntu 20
Webmin version Latest

Trying to update OS I get this warnings. Seems to be Virtualmin related

W: http://software.virtualmin.com/vm/6/gpl/apt/dists/virtualmin-focal/InRelease: Key is stored in legacy trusted.gpg keyring (/etc/apt/trusted.gpg), see the DEPRECATION section in apt-key(8) for details.
W: http://software.virtualmin.com/vm/6/gpl/apt/dists/virtualmin-universal/InRelease: Key is stored in legacy trusted.gpg keyring (/etc/apt/trusted.gpg), see the DEPRECATION section in apt-key(8) for details.

What you do is run this command:

sudo apt-key list

It will give you this:

pub   rsa4096 2017-05-01 [SC] [expires: 2024-04-29]
      E36F 0664 7D8E BD2B E364  2BCE D9F9 0107 60D6 2A6B
uid           [ unknown] Virtualmin, Inc. (Package signing key for Virtualmin 6) <security@virtualmin.com>
sub   rsa4096 2017-05-01 [E] [expires: 2024-04-29]
...

You take the code at the end 60D6 2A6B and remove the space, and use the domain of the email to get the below:

sudo apt-key export 60D62A6B | sudo gpg --dearmour -o /etc/apt/trusted.gpg.d/virtualmin.gpg

Ignore apt-key is deprecated, it is why you are getting this in the first place, but once you know this trick, you can fix most issues like this since it affects all repositories.

Hope that helps.

Flesh.

warnings are not errors. so in general, this can be ignored.
but anyway, i believe newer virtualmin versions fix this, see a newest announcement here :

if i read the newest install script correctly, it removes older keys in trusted.gpg and inserts new in /usr/share/keyrings similarly to the workaround from @rremelin above.