I’ve built from 18.06 with the patches on github, and I’ve built the gl-inet version of openwrt from github. Neither of them produces a tar file. The sysupgrade.bin file doesn’t verify. Are these expected to work?
After doing some more reading of a previous thread I realized that I didn’t need to use u-boot, so I have been able to install a patched openwrt 18.06. Thanks for your help on this!
It would be good to figure out what’s going on with u-boot, though. As it stands, if I don’t have Windows (and I literally do not have Windows, I’m not exaggerating), there is no way to de-brick the device if I brick it.
I was in the same situation, with no Windows available. It is conceivable that one could, somehow, flash a new boot loader over serial, but that is too risky, even for me.
In the end, I used a friend’s Windows machine (and brought an Ethernet cable and an USB Ethernet adapter and drivers, just in case). The process, from walking up to thanking them, took under 15 minutes, being very careful with each step.