rhel-*-optional-rpms' does not match a valid repository ID (installing remmina)

Hello-

I am trying to get remmina installed on RHEL 8 and am having a bear of a time. I am not a Linux guru so bear (sorry) with me. I am going through a procedure at 'https://snapcraft.io/install/remmina/rhel' and when I get to the point of entering this command: sudo subscription-manager repos --enable "rhel--optional-rpms" --enable "rhel--extras-rpms"
sudo yum update I get the errors:
rhel--optional-rpms' does not match a valid repository ID
rhel--extras-rpms' does not match a valid repository ID

I went through /etc/yum.repos.d and eliminated any repo that referred to '7'. I searched and do not find any specific article that is similar to the errors for RHEL 8. What could be the issue?

The system is correctly registered with Red Hat.