Thanks for that!! Um, well, the news from this afternoon is that I now have 12.3 running, still with OC 7.6. It was one of the onboard LAN ports that froze it as it came through to desktop. Basically seems to be Onboard Lan Controller #2. Onboard 1 is enabled, but does not appear. Wifi takes a few attempts (delete and re-join) to get connected. I'll have to do some digging. Previously the Intel Lan port worked OOB, as did the WiFi, so not sure what is going on. Ok, further investigation tonight and I found this in the OC guide.
The boot-arg for enabling Intel I225-V ethernet controller has changed since macOS Monterey 12.3.
Use e1000=0 instead of dk.e1000=0.
This allows you to get through to the desktop without freezing when Onboard Lan#2 is enabled in Bios, but the previously working I225-V Ethernet continuously connects then drops connection. Brings me back to an update to OC 8.0 and seeing if I can get the 10gbe Lan working.