$ zypper in python310-libmount

    ...

    $ zypper info python310-libmount

    ...
    Repository     : Main Repository (OSS)
    Name           : python310-libmount
    Version        : 2.38.1-10.2
    Arch           : x86_64
    ...

    $ rpm -ql python310-libmount

    ...
    /usr/lib64/python3.10/site-packages/libmount/__init__.py
    ...

    $ ls -l /usr/lib64/python3.10/site-packages/libmount/__init__.py

    lrwxrwxrwx 1 root root 53 Mar 19 15:41
/usr/lib64/python3.10/site-packages/libmount/__init__.py ->
../../../python3.9/site-packages/libmount/__init__.py

That file does not exist unless python39-libmount is installed, so it's a
broken symlink and
`import libmount` does nothing. Python seems to just treat it as an empty
package.

The python39-libmount package has the correct contents for the file, and
installing it makes the symlink
work and allows the package to be imported, so it's just the python310- package
that's broken.