My Ubuntu install was nice enough to tell me that the 21.10 version had finally been released! So like any good upgrade-addict, I gave it a whirl!
It broke docker.
Which was the only thing really running on the Pi. However, it was also hosting my blogs.
Through many searches, I finally stumbled across this post on IssueExplorer.com, and it’s exactly what I needed.
sudo apt install linux-modules-extra-raspi
Evidently, this only affects the Rasberry Pi install of Ubuntu.