Installing encrypted Kubuntu - no Key slots available?

While setting up a new computer with Kubuntu 20.04 (encrypted LVM) and Yubikey, I came across a problem I am not able to solve myself. I am looking for the 8 key slots, Kubuntu should show when entering the followin:

sudo cryptsetup luksDump /dev/sda5

On my working computer, it shows which slots are enabled and which aren't. But on the new device it only shows the following:

$ sudo cryptsetup luksDump /dev/sda6

LUKS header information
Version:        2
Epoch:          3
Metadata area:  16384 [bytes]
Keyslots area:  16744448 [bytes]
UUID:           caf83123-8ea3-44fa-aeda-36a2525c96bf
Label:          (no label)
Subsystem:      (no subsystem)
Flags:          (no flags)
Data segments:  0: crypt
        offset: 16777216 [bytes]
        length: (whole device)
        cipher: aes-xts-plain64
        sector: 512 [bytes]
Keyslots:  0: luks2
        Key:        512 bits
        Priority:   normal
        Cipher:     aes-xts-plain64
        Cipher key: 512 bits
        PBKDF:      argon2i
        Time cost:  4
        Memory:     910336
        Threads:    4
        Salt:       45 80 a9 52 90 b9 8f a4 e1 ef b9 1e d9 9a 06 f0 
                    c5 93 21 73 e6 d2 d5 2b 21 d4 ff 99 c3 86 1b 63 
        AF stripes: 4000
        AF hash:    sha256
        Area offset:32768 [bytes]
        Area length:258048 [bytes]
        Digest ID:  0
Tokens:
Digests:
  0: pbkdf2
        Hash:       sha256
        Iterations: 98550
        Salt:       ac d4 9f 3c 92 12 1d 7f 05 43 9d 7d a1 53 41 8f 
                    2f f9 86 cf 6c 4e 4d e1 9d 8a f5 f8 8b d8 7c 46 
        Digest:     02 51 f5 53 81 aa 99 44 d6 7c 4e 86 19 3d c8 bf 
                    21 6f 11 4f 4b 9a 5e bb 5a d4 72 6f d0 3b 49 e3 

QUESTION: What did I do wrong? Why is cryptsetup not showing the 8 key slots with which I can setup the yubikey?