Looks like some component of your system blocks while trying to obtain random data from the kernel (i. e. reading from
/dev/urandom or calling
getrandom()) due to insufficient entropy (randomness) available.
I do not have a ready explanation for why the problem depends on a particular kernel version, or which component on your system actually blocks, but regardless of the root cause,
Indeed, as pointed out by Bigon in his answer, it appears to be a kernel bug introduced in 4.16:
This bug is introduced by the "crng_init > 0" to "crng_init > 1"
change in this commit:
This change inadvertently impacts urandom_read, causing the
crng_init==1 state to be treated as uninitialized and causing urandom
to block, despite this state existing specifically to support
non-cryptographic needs at boot time:
Reverting 43838a23a05f ("random: fix crng_ready() test") fixes the bug
(tested with 4.16.5-1), but this may cause security concerns
(CVE-2018-1108 is mentioned in 43838a23a05f). I am testing a more
localised fix that should be more palatable to upstream.
...Still, you may try using
rng-tools to gather entropy faster.