This was always a concern for me when cPanel announced that they would begin supporting Ubuntu. Would there be enough users to warrant continued development in Ubuntu? It's hard to justify spending a lot of time with Ubuntu if there are only 5 users using Ubuntu+cPanel.
If memory serves, the Ubuntu support came about after the CentOS 8 short lifespan announcement. But before AlmaLinux and Rocky Linux were announced as potential successors to CentOS. Once a free RHEL-variant came about, the need to support Ubuntu probably wasn't seen as necessary.
Now with the recent RHEL source package announcement, this is once again bringing Ubuntu/Debian support into the limelight.
I've been preaching just about every where I can find a soapbox, for a Debian based Enterprise level Linux distribution. The one thing that Debian is missing when compared to RHEL or the various RHEL-variants (at least as far as I know) is an extended lifetime. CentOS releases (at least CentOS 5-7) had 10 year lifespans. I believe AlmaLinux and Rocky Linux have also promised 10 year lifespans for 8.0 and 9.0 respectively (although given the RHEL source announcement, it remains to be seen if they will be able to fully honor that).
If you ask me, the market is ripe for some entity to create a Debian-based Enterprise Linux with a 10 year lifespan. Unless there is something that I am not aware of that would prevent this.
Debian LTS releases now have a 5 year lifespan. Ubuntu LTS releases also have a 5 year lifespan. Ubuntu does have a paid option where they support LTS versions for 10 years, but if you're going to pay for the OS, why not just use RHEL? While Debian and Ubuntu can do in-place major OS updates, I'm not sure if that's wise in a real production environment. I would also lean more towards a pure Debian base as opposed to Ubuntu. Ubuntu being owned by Canonical, means they could potentially pull a stunt like RHEL has done.
A 10 year life-cycle Debian-based distribution could become the go to distribution for cPanel and other web hosting control panels. Let's face it, the majority of cPanel server administrators don't really do a whole lot with the underlying OS - if the task can't be done in the WHM or cPanel then it can't be done. What OS cPanel is running on top of really doesn't matter as long as cPanel is dedicated to developing to work on the OS. But the one thing the OS needs is longevity. Nobody wants to be updating to a brand new OS every year.