Warning: Enforcing GPG signature check globally as per active RPM security policy (see ‘gpgcheck’ in dnf.conf(5) for how to squelch this message)

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gpgcheck can be set globally (in [main] of dnf.conf) or per repository.
Removing spaces is correct.

      gpgcheck
              boolean

              Whether to perform GPG signature check on packages found in this repository.  The default is False.

              This  option can only be used to strengthen the active RPM security policy set with the %_pkgverify_level macro (see the /usr/lib/rpm/macros
              file for details).  That means, if the macro is set to 'signature' or 'all' and this option is False, it will be overridden to  True  during
              DNF  runtime,  and  a warning will be printed.  To squelch the warning, make sure this option is True for every enabled repository, and also
              enable localpkg_gpgcheck.

Note the specific instructions on squelching the warning, and why it
arises.

You need to check the manpage in the qube you are using for dom0 updates
(likely Fedora 33 based), not in dom0.