What about missing (diabled) functionality?

After the removal of bcachefs, the following options are no longer enabled in my .config (they were selected by BCACHEFS_FS before):
XARRAY_MULTI
CLOSURES
MIN_HEAP

Missing CLOSURES and MIN_HEAP are easy to handle, as the bcachefs module can just include a copy.
But XARRAY_MULTI has a big impact on how xarray works, and can't easily be bolted-on from a module.
How does DKMS handle that?

XARRAY_MULTI is also selected by a few other options (e.g. HUGETLB_PAGE, TRANSPARENT_HUGEPAGE, and ZONE_DEVICE), so most distro kernels on x86 may have it.