At first it seemed that the update had succeeded without a hitch; however, on restarting my computer, it would no-longer recognize my router. Both the wired ethernet connection (which is what I normally use) and the both of my wireless networks (2.4GHz & 5.0GHz, both from the same router as my wired network) were all invisible. Even attempting to connect Firefox to “192.168.63.72” in order to check the configuration of my router also failed; I got “there is no router at that address”. But yes there is!
I tried restarting the cable modem, router, and computer multiple times, but the OS still couldn’t see the router.
So I had to use Timeshift to reset my system back to how it was on September 13, then everything worked again.
UPDATE, 3 hours later: I managed to fix the issue. Somehow, my router got reset to “factory”! I’m not sure if this happened before, during, or after the latest Manjaro upgrade process on my main computer.
I noted that the 2 other computers I have running Manjaro (not yet upgraded) were able to connect, as was my main computer after timeshifting back to September 13. However, on looking at their IP addresses, instead of being on the 192.168.63.## subnet as I expected, they were on the 192.168.1.## subnet! No wonder I couldn’t connect to 192.168.63.72; Firefox was right: there really was no router at 192.168.63.72 because it got moved to 192.168.1.1.
After redoing all my router settings, I was able to do this latest Manjaro update on my main computer, restart, and access my router & network and the Internet with no problem.
I think the issue may be that the way Manjaro reacts to a “router not on expected address” may have changed; my not-yet-upgraded Manjaro installations were able to connect via something called “auto-ethernet”, but my upgraded machine couldn’t connect at all. Maybe that’s even a “feature” rather than a bug; could have a security benefit, I suppose: if an unauthorized person were to screw-with the router, apparently Manjaro now balks; whereas before, it would connect to whatever IP the router’s DHCP server was offering, without complaint.