The naming conventions for network interfaces on stage1 and stage2 must match.
See also: https://lists.altlinux.org/pipermail/make-initrd/2021-September/000568.html

In the future, will need to modify generate.mk so that can set all
the variables in this config.

This is an alternative to the initrd-propagator feature.
bootchain-* is a make-initrd features. You should look at the documentation
for it in the make-initrd-bootchain-* packages:
/usr/share/make-initrd/features/bootchain-*/README.md