After applying FDE on the system, it takes very long until grub opens the
(small) boot partition on a nvme disk. Reason is most probably how grub handles
the necessary hashing of passwords
(https://linux-blog.anracom.com/2018/11/30/full-encryption-with-luks-sha512-aes-xts-plain64-grub2-really-slow/#more-8488
- see Conclusion 2).

Example:

# df -h /boot/
Filesystem              Size  Used Avail Use% Mounted on
/dev/mapper/boot_crypt  233M  120M  109M  53% /boot

cryptsetup luksDump /dev/nvme0n1p1
...
Key Slot 0: ENABLED
        Iterations:             3628290
...

Key Slot 1: ENABLED
        Iterations:             3634578

I would appreciate, if this rather high delay (even on a Ryzen 7 1700X CPU)
could be seriously reduced - the kernel loads this (and many more) partition
quite imperceptible.