Not working with encrypted boot partition.

[ChrTall]

I have an encrypted luks1 /boot partition. I enter a password to get to the grub boot menu.
Then when I select a Kernel I have to provide a different and long passphrase which unlocks my root partition. (luks 2)
The /boot has a second slot which is a key file in the root partition to avoid having to unlock the /boot partition again after already unlocking it in grub stage 1.
I wanted to use the yubikey to unlock the root partition, but I am not getting prompted for the yubikey and it does not work.
Does anybody know if this is possible?
I do not plan to use the yubikey to unlock the /boot partition for grub stage 1, because this is not possible as far as I know.