Reviving the Tessel 2 - The Big Bang That Failed

At the end of the last post I decided that upgrading OpenWrt was worth the risk. There was a current upstream release, the Tessel's MT7620 hardware still belonged to a supported OpenWrt target family, and the factory image had been without security updates for about a decade. I also had an acceptance test: the board had to boot, the Tessel bridge had to start, the CLI had to connect, JavaScript…