Booting Rocky 9 on old Mac Pro

Thank you @iwalker . Rocky 8 presented the same behaviour. I struggled to install because of an issue getting it to accept the system destination hard drive, and when it actually completed the installation process, it failed to boot the system.
I put the question to a release engineer a moment ago. I hope to learn enough to overcome this issue and see if DaVinci Resolve will run well enough on Rocky 8.6 or higher, on my old machine.
Here’s the post I just wrote: Rocky Linux 9.3 Available Now - #8 by Lortega70
Thanks and best regards,
Leo