Well, that was probably the dumbest problem I've had in a while.
TL;DR: I updated from nvidia graphics driver 550 to 570 on my Ubuntu 24.04.1 LTS gaming machine. Networking stopped working. A few google searches suggested that a few packages that were needed might have been left out when it updated the kernel for... Reasons (tm).
You know, things like... networking. Oops. Lemme just download the missing packages and- ah. right. Damnit.
The end solution was to use grub to boot into the previous kernel's recovery, use dpkg to find and correct missing packages. (Pro tip: Hit 'enable networking' before doing this or it won't work.) It wound up taking about two minutes to find and install the missing packages and enable my fully armed and operational battlestation.
Here's the thing: This is an *old problem.* I have search results going back four years of people having this issue. How is this still a problem? *WHY* is this still a problem?