This issue also affected Linux Mint 19.2, and Brian's workaround and fix in #36 work for that distribution as well.
I used the workaround steps to resume the broken boot, then followed the fix steps and rebuilt the initramfs using:
# rebuild initramfs /usr/sbin/update-initramfs.distrib -u
then copied the resulting .img to my netboot server.
This issue also affected Linux Mint 19.2, and Brian's workaround and fix in #36 work for that distribution as well.
I used the workaround steps to resume the broken boot, then followed the fix steps and rebuilt the initramfs using:
# rebuild initramfs update- initramfs. distrib -u
/usr/sbin/
then copied the resulting .img to my netboot server.