Apparently I bricked my WNDR3700v4 with a broken feature-rich image.
Cannot connect with TFTP, and nmap finds no host in 192.168/16 and 10.0/15. Cannot see an Ethernet address in arp either, but that might be me.
Cannot enter failsafe mode because the power LED turns from amber to off instead of green (tried anyway). This is probably when the image crashes.
Obviously cannot sysupgrade from command line or luci either.
Do I have to get a serial cable? Anything I can still try without opening the case?
Backstory: The official BB image for a WNDR3700v4 only provides 14MB of 128MB flash. I tried to work around this by flashing a CC image followed by a sysupgrade to BB without keeping the configuration. Seems I picked a broken image. Developers, please REMOVE BROKEN IMAGES from the servers before they do further harm.