So an update on this. I tried again this morning, but instead from latest Linksys FW 22.214.171.124968. This time after first reboot of the router and cycling through the blue LEDs once, the Linksys logo started flashing. I thought I had bricked the router, but left it alone and eventually it came solid. Opened browser to 192.168.1.1 and was presented with openwrt.
Only other thing different this time was I was plugged into ethernet port 8. Yesterday was plugged into port 4.
I like the basic inclusions like PPPoE and Luci to get the WAN back online nice and quick.