0.6.40 at least booted for me... it was the first image since 0.6.27 that actually booted up instead of crashing and burning early on. However, I had no IPv4 networking and apparently had an IPv6 address which was non-responsive.
0.6.41 was pushed several hours ago, and reverts some tx/rx gmac changes that must have crept in re-syncing with the rockchip kernel, and I now have networking... so the fix if you've just installed 0.6.40 is to update to 0.6.41, or you can probably decompile the DTS, make the changes in this commit, and recompile it if you have already configured the system, but you won't get the DMA changes that are also in 0.6.41.
SD Boot - quick ping test at the end:
https://pastebin.com/MgvwcW2m
eMMC boot - ping and iperf test at the end:
https://pastebin.com/piGuwGmD
Based on what I've seen so far, I'm happy moving over to this image as the base image for the rock64 I use all the time.
I just need to check something related to the memory, as I think one of the boards I have is being over or under-reported as to memory size... need to boot to an older image to see what is going on there. Just me, the board I had thought was 1GB was actually a 2GB board...