sbsign doesn't work with tpm2-openssl

[mittwerk]

sudo sbsign --key "/var/lib/shim-signed/mok/secureboot.priv" --cert "/var/lib/shim-signed/mok/secureboot.pem" --output "/boot/vmlinuz-6.7.8-1-liquorix-amd64" 

Can't load key from file '/var/lib/shim-signed/mok/secureboot.priv'
40476D8ADA700000:error:1E08010C:DECODER routines:OSSL_DECODER_from_bio:unsupported:../crypto/encode_decode/decoder_lib.c:101:No supported data to decode. Input type: PEM