I went ahead with the firmware update. Hit restart or reboot, whatever it said. Now I'm stuck in a boot loop that doesn't get past the splash screen to the boot animation. Then powers off, and immediately restarts. One boot/power off cycle takes about 13-14 seconds. Holding any key/button combinations seems to be of no help. Additional information! I was rooted with magisk. Two failed attempts to install the new firmware, so I flashed the original boot image back to the device and rebooted. That went no problem. Tried the OTA update one more time. This time I didn't get an error message at the end of it. Phone restarted, and here I sit 6 hours later, hoping the battery eventually drains so I can try ADBing in. If anyone has any suggestions, I'd appreciate it. Something I'm noticing as I'm typing this, just as the phone powers down, the screen has a glitch-in-the-matrix style flicker. I doubt that really means anything to anyone, but just in case.
A pre-thanks to everyone!