I can understand not wanting to do an operating system major version migration every ~3 years. (I am a Fedora Linux user, so I know the pain – even with how easy they have made it – of doing a sysupgrade every year.)
I presume a near future release of Foreman will run on CentOS stream 9. I guess if people do not want to participate in the CentOS Stream community because of 9’s life cycle being too short, and things do not seem to work on the downstream distribution re-compiles of Red Hat Enterprise Linux (RHEL), one could sign up for the no-cost RHEL Individual Developer Subscription to get RHEL for free. If one is using RHEL & Foreman in a corporate setting, one could talk to a Red Hat sales person about getting Red Hat Developer Subscription for Teams.
(Full disclosure: I am a Red Hat employee, but not intending for this to be an ad. I am just wanting to inform of alternate options.)