NK3 needs to be told in advance what kind of key type will be installed in one of the 3 slots provided by the OpenPGP card standard.
I like to use openpgp-tool from OpenSC to check, for example on my card I have the following now:
> /usr/local/bin/openpgp-tool -K
Using reader with a card: Nitrokey Nitrokey 3 [CCID/ICCD Interface] 00 00
Aut Algorithm: EDDSA
Aut Create Date: 2023-12-22 19:13:34
Aut Fingerprint: 2d:95:41:9c:2c:47:7a:bc:a1:e7:dc:d9:c1:4a:88:c5:c3:07:dd:91
Dec Algorithm: ECDH
Dec Create Date: 2023-12-22 19:13:34
Dec Fingerprint: cb:3d:95:9e:63:62:15:2a:da:d3:9f:c3:56:6d:12:69:b6:52:8e:d3
Sig Algorithm: EDDSA
Sig Create Date: 2023-12-22 19:13:34
Sig Fingerprint: f2:ee:32:6f:54:2b:78:44:22:b4:fd:10:33:fb:9d:a8:17:64:f4:7a
I guess after the hardware reset it is undefined so you can upload what you want.
You can change the key type with the -t option of the openpgp-tool.
In general, using pkcs11-tool to manage keys on the OpenPGP card can be confusing in my opinion. I prefer openpgp-tool (best to view, can generate only RSA keys) or one of the options to manage cards with gpg2 or gpg-card.