Tried again with 22.04. Same IPs, same server name, less CPU and Memory allocation.
Took 40 seconds until the bullding PHP chroot environments message popped up, then the computer was essentially idle until the 41 minute mark. Then top showed a bunch of dpkg processes firing off, load went to 4, and 20 seconds later the process looked complete. But again, the panel server thinks the machine in question has the IP address of the gateway.
I'll try again when less tired.