Ah, yeah I agree it is a bit odd.
For reference, here is the dependency chain that meta-amd adds that requires x11. Specifically libdrm:
ERROR: Nothing PROVIDES 'libxrender' (but /code/balena-amd/build/../layers/meta-amd/meta-amd-bsp/recipes-graphics/drm/libdrm_git.bb DEPENDS on or otherwise requires it)
libxrender was skipped: missing required distro feature 'x11' (not in DISTRO_FEATURES)
NOTE: Runtime target 'plymouth' is unbuildable, removing...
Missing or unbuildable dependency chain was: ['plymouth', 'libdrm', 'libxrender']
ERROR: Required build target 'resin-image-flasher' has no buildable providers.
Missing or unbuildable dependency chain was: ['resin-image-flasher', 'resin-image', 'plymouth', 'libdrm', 'libxrender']
From what you are saying, I take it the recommendation is to find a way to remove libdrm?
The network-manager and related issues seem to be because some of the bitbake files assume that BASE_LIB is lib and break if it is lib64