Nikon finally released firmware updates for the D5, D850, and D500 to allow them to use CF cards.
https://www.nikonrumors.co/nikon-d5-d850-d500-firmware-updates-released-add-cfexpress-card-support/
https://www.nikonrumors.co/nikon-d5-d850-d500-firmware-updates-released-add-cfexpress-card-support/