Based on the coming official announcement in https://issues.redhat.com/browse/OCPSTRAT-1865, the support for RHEL worker nodes will be removed in OCP 4.19. Consequently, for existing OCP clusters (version 4.18 or earlier) with RHEL worker nodes, it has become technically infeasible to perform a complete cluster upgrade (including RHEL workers) to version 4.19.

Theoretically, in such scenarios, prior to upgrading the cluster to 4.19, users should:

1. Migrate workloads from RHEL worker nodes to RHCOS nodes
2. Remove all RHEL worker nodes from the cluster
3. Start the OCP cluster upgrade

Therefore, we strongly recommend that the CVO implement an upgradeable condition check that would:

• Automatically block cluster upgrade to 4.19 by default when RHEL worker nodes are detected

• Require administrative confirmation to continue the cluster upgrade

I'm not sure about the feasibility of implementing this functionality and whether it aligns with the OTA team's technical roadmap. Any feedback or suggestions would be highly appreciated.

Thanks.