This code repository offers downloads for the latest images of various DevTerm models, as well as kernel patches, keyboard firmware, the source code for screen and printer drivers, hardware schematics, assembly instructions, and essential technical documents.
This creates the file lib.config with one line: KERNELBRANCH='tag:v5.10.60'
This forces the build system to use the 5.10.60 kernel sources only.
I also updated the readme to perform a proper build.