Grub2 updates for Red Hat systems are making some unbootable

This is the official page for RedHat, with the full troubleshooting and recovery steps: https://access.redhat.com/solutions/5272311 (found in the links in the bugzilla page).

Excerpt:

"Red Hat is aware of this bug and is working on a fix.

DO NOT apply the affected Errata RHSA-2020:3217 for RHEL 7.
DO NOT apply the affected Errata RHSA-2020:3216 for RHEL 8.

For Red Hat Satellite exclude this Errata from your Content Views"