I tried to figure out what to do, without coming back here. I eventually got a build. Trying to see if there are updates to cwhe17's tree bring no joy. All I get from git, is I have no idea what you are talking about. My guess is that I am missing some config file variable, or some environment variable. But as mentioned below, spring is coming and I don't have time to try things.
Instructions as to how to proceed past that point, are lacking. It seems that output/images (or something like that) contains an image. (and some txt file about this). Everybody and their dog talks about how perfect etcher is. I'm sorry, I disagree. If you run etcher as some non-root user - you get some error message which makes no sense, and doesn't point to the actual problem being that you need to be root to run this program. Why can't etcher look to see if it has permissions, before doing things (and generating this stupid error message?)
Fine wrap etcher in sudo, and it works. Supposedly no mistakes.
I boot the microSD, and no display. I plug in ethernet, and do it again, hoping that maybe there is a SSH login. NMAP can't find this host on my LAN, so if the kernel starts, it doesn't get to the point where the NIC is configured.
I don't have a serial cable to see if there is boot messages to serial.
I would love to work on this more, but spring is approaching. (I live on a farm.)
If someone has a pointer to an image which might allow btrfs and lets the display work; that would be wonderful. I could then try to update various other hardware. If I get a rainy day, I could drop my btrfs desire to ext4.
My ptp device needs an upgrade. My router is too out of date, and so it is to be replaced by a new device. But surely I can configure this device from something like a laptop before I switch wires? :-)
It may be that I need to wait until next winter, to find time to pursue upgrades.
Thanks to all, even if I am too stupid to figure out what to do.