Comment 16 for bug 1833604

So, to summarize:

GA and HWE kernels in Ephemeral == no drivers for DCPMMs
GA and HWE kernels in installed OS == drivers for DCPMMs

Just on a lark, I booted the 4.15 kernel ephemeral and tried installing linux-modules-4.15.0-55-generic and while they do get installed, they're not loadable due to something about missing symbols.

/var/log/apt/term.log:Setting up linux-modules-4.15.0-55-generic (4.15.0-55.60) ...
/var/log/apt/term.log:Setting up linux-modules-extra-4.15.0-55-generic (4.15.0-55.60) ...
ubuntu@lenovo-sr650:~$ find /lib/modules/4.15.0-55-generic/kernel/drivers/ -iname "*pmem*"
/lib/modules/4.15.0-55-generic/kernel/drivers/nvdimm/nd_pmem.ko
/lib/modules/4.15.0-55-generic/kernel/drivers/dax/dax_pmem.ko
ubuntu@lenovo-sr650:/lib/modules/4.15.0-55-generic/kernel/drivers/nvdimm$ uname -a
Linux lenovo-sr650 4.15.0-55-generic #60-Ubuntu SMP Tue Jul 2 18:22:20 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
ubuntu@lenovo-sr650:/lib/modules/4.15.0-55-generic/kernel/drivers/nvdimm$ sudo insmod nd_pmem.ko
insmod: ERROR: could not insert module nd_pmem.ko: Unknown symbol in module
ubuntu@lenovo-sr650:/lib/modules/4.15.0-55-generic/kernel/drivers/nvdimm$ sudo modprobe nd_pmem.ko
modprobe: FATAL: Module nd_pmem.ko not found in directory /lib/modules/4.15.0-55-generic