Despite being a debian/ubuntu guy, I usually used CentOS for production deployments because it would be easy and seamless to upgrade to RHEL when I hit the big leagues.

Not anymore. I just use the latest ubuntu LTS and call it a day.

IBM/RedHat was soo predictably short sighted on this.

The free LTS/distro and pay for support if you feel like it never really worked financially. Maybe Canonical is profitable at this point. It's not Red Hat (or SUSE for that matter.)

There are many large organizations that pay for RHEL support. Supercomputers, for example. These organizations also benefited from being able to spin up analog installs of CentOS on local machines for testing. Not anymore. I expect RHEL's market dominance in these areas to diminish over time.

For testing environments Red Hat will literally give them free RHEL. Problem solved.

No, they won't. I'm talking about the users of HPC centers, not the maintainers. The supercomputer cluster is at NASA or DoE and running RHEL, but the user is some grad student in Caltech or whatever. The grad student needs the analog environment to run their code before their scheduled time on the big iron.

HPC was always a tough sales area for Red Hat and RHEL.

In general, while RHEL is obviously still an important revenue source, there's also a lot of focus on OpenShift going forward which has done of pretty good job of covering (and more) inevitable RHEL declines moving forward.

All the HPC I've used in the past was always RHEL... I wouldn't have imagined it was a tough sales area for RedHat, at least in the past.

So you say "it would be easy and seamless", but did you ever actually do it and upgrade to RHEL? Because most people throw that out as a supposed sales pipeline that was lost, but the real life metrics indicate that almost never happened.

In one case, yes.