Problem found and solved. It was all a matter of searching Google with the right keywords (“poweredge r710”, “uefi”, “linux”). I found this article: https://www.dell.com/community/PowerEdge-Hardware-General/Dell-PowerEdge-R710-and-RHEL-6-2-UEFI-enabled/td-p/3836482/page/2 which says, “RHEL 6.2 and the PERC 6/i RAID controller have issues booting a GPT partition over a certain size (we’re guessing 2 TB, but that’s just a guess).” I had been trying to install AlmaLinux on a single 4.5TB virtual disk. After reconfiguring so that I had a 48GB virtual disk for the OS and the rest of the space for file storage, AlmaLinux 8.5 installed and booted correctly.
Hopefully my experience will help someone else in the same situation.
---Bob.