I discovered your excellent work with letux, and thought I could see if I could help out.
I'm hoping to get postmarketOS running on my 1ghz pandora, using the letux kernel. So far I've successfully built and booted your 5.10 kernel and got wifi and keyboard working with no modifications on my...
I am able to boot the 5.10 letux kernel, I'm cowardly booting off an SD-card.
The thing which solved it for me was to do mkimage for uBoot, and I couldn't get the dtb appended correctly so i just added it on the side.
setenv bootargs root=/dev/mmcblk0p2 rw rootwait vram=6272K...
Well, where to start?
I use it a lot as a USB disk at work, working with documents, the odd bit of programming on the go.
Off work I use it mostly to lose sleep over OpenTTD and the excellent ports of the DOS X-COM games.
I used to use it a lot as a USB-CDROM to rescue crashed computers, but...
On your debian machine make the usb0 stanza like this in /etc/network/interfaces:
iface usb0 inet static
up iptables -A POSTROUTING -t nat -s 192.168.1.0/25 -j MASQUERADE
A while ago, I made a hackish perl script which did the same thing as your app, except I used it exclusively for booting pcs.
I lost the script, but I remember having problems on one of the kernels, probably the 2.6 one, and one of the modules was not working for me, I don't remember if it was...