Ok, original issue is fixed. I had BOARD_NAME instead of BOARD in my userpatches config. Now ./compile docker myconfig works.
Thanks a lot, but with the network issue I think I can find a workaround with some little hint from you.
Actually, what I'm trying to achieve is customizing image. I copied config/boards/lime2.conf to config/boards/myboard.conf, renamed the BOARD_NAME="MyBoard" to change the default hostname. BOARDFAMILY and BOOTCONFIG are the same as for Lime2, it is the nearest compatible board, original Lime2 build works fine. The desired image should include some pre-installed stuff (Node.js 10x, my app, dependencies), I did it with customize-image.sh. Now setting BOARD=myboard creates the image I need, with the changed hostname and preinstalled software, but the network does not work. Obviously, some patches are BOARD -depended, not the board family. Workaround is leaving BOARD as is, and renaming the host in customize-image.sh script. And here I need a hint - hostnamectl does not work in build time, what is the better approach?