All,
Well, I finally hooked up my dead Raspberry Pis to a monitor to see what is going on with the Pi nodes being unreachable. It turns out I had turned off the dhcpcd service for some reason. Little did I realize that the static IP is located in /etc/dhcpcd.conf, so when I rebooted -- boom -- no networking, and _no net working_.
I think I was trying to do something froggy, like run DHCP on the router. K3S doesn't run with dhcpcd running, so maybe I was debugging that, too. It was 4 years ago. Who knows.
Anyway, one of the nodes has some sector read errors while booting up. I transferred the SD card to an Ubuntu laptop to run fsck, and fsck said everything is hunky dorey. I booted back up with the SD card, and I saw the same sector errors again.
What the heck, fsck. It is two different architectures, but it's just an ext4 file system. Shouldn't matter at all. Login takes 30 minutes now. :(
Ben