On my NK3 PIV I would like to import a P12 which contains a private key and an S/Mime Cert. This is currently not possible (denied with operation not supported).

While I understand that a private key should live and die on a device only, this is not very budget friendly. It forces me to buy multiple S/Mime certs for one email address as I need a private key and certificate request per device. Assume that I like to have my S/Mime cert on multiple devices for backup and convenience reasons.

Yubikeys allow the user to import P12 files with cert and private key which originates elsewhere. So I only have to pay for one cert and can use it on multiple devices.