As for the actual culprit, there are not that many things in the initramfs which use libudev1; most of them are from cryptsetup, but the most likely one is sbin/wait-for-root. This also has ubuntu specific modifications, so it's very likely that this doesn't get along with SOCK_NONBLOCK.
As for the actual culprit, there are not that many things in the initramfs which use libudev1; most of them are from cryptsetup, but the most likely one is sbin/wait-for-root. This also has ubuntu specific modifications, so it's very likely that this doesn't get along with SOCK_NONBLOCK.