I've not had much luck today...

I repurposed an old SSD, installed a APFS partition, downloaded Monterey and tried to install on the external drive. No good. Cloned my start up drive to the SSD, booted from the SSD and ran the Monterey installer again. I kept getting kernel panic and an endless cycle of rebooting.

Now I'm downloading Big Sur to see if I have any luck with that.

The only thing I could do that I am not doing is to install from Software Update directly to my start up drive and I'm not willing to do that.

Any advice? Thanks.

iMac (19,1, 3.1 GHz i5, 12.7.4, 40 Gb RAM); MacBook Air (1.8 Ghz, 8 Gb RAM, 10.14.6, 256 Gb SSD) Vodafone router and Devolo Wi-Fi Extender, Canon TS8351 printer/scanner.