There were no replies to this question. After digging in a bit, I found a way to make it work. I made two changes, and it is not clear whether one or the other – or both – were needed.

Change one – Upgrade to VirtualBox 7.0.6. Among the items listed in the changelog for this version is compatibility with RHEL 9 guests.

Change two – In the Settings – Basic screen of the guest I changed its type from “RedHat 64-bit” to “RHEL 9.x 64-bit.”

The ISO for network install booted and ran through with no errors.

Hopefully others can benefit from my experience.

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Bill Gee