Uploaded the squashfs-factory.bin (changed to .img) firmware via web admin as adviced in the wiki but the router doesn't respond at all now.
No ping on 192.168.1.1 (on a router and direct link with manual ip set). Nothing on nmap or nmrpflash.
I tried netcat for udp... Reset btn doesn't work anymore.
Is serial/parallel connection my only resort?
An IPv6-capable "desktop" may see the router as a neighbor as one way to "find" it if it's up. Checking with tcpdump or wireshark may also reveal if it is alive at all.
I ended up in the same situation. Flashed the openwrt-18.06.2-ramips-mt7620-ex2700-squashfs-factory.bin via the web interface and now there's no DHCP response and no ping response from 192.168.1.1 if I configure 192.168.1.2 for my PC manually...
Did you get yours working?
Give it a shot. You might be surprised how easy it is. I bought this one , but any conpliant ftdi should ‘just work’ on a linux machine as drivers are in the kernel