Also, does the original lan and dhcp still exist? And did you setup a management interface of any sort?
I was able to get it to recover using the Uboot method and the router is operational. My issues was that I was using the wrong ip (192.168.0.1 was what I should had used not 192.168.1.1)
However, I have tested it again and again. I cannot get into fs mode with this version. I sniffed both ports and don't see the UDP traffic. I've done the tcpdump and saw nothing. Am I using the wrong version? Fortunate its not that hard to do the Uboot method - but still a little concerned for the next person (and you have to blow everything away to do it).
This is the version I am using:
openwrt-23.05.2-ramips-mt7621-tplink_deco-m4r-v4-squashfs-factory.bin