Nikon released a minor update to the Z9 firmware (version 5.20), with one new ability (support for NX Field), a renamed custom setting, and a series of small bug fixes.
They also released a minor update to the Z50II firmware (version 1.01), with one new ability (support for pre-release capture using a Smallrig SR-RG2), the same renamed custom setting, and a series of small bug fixes, including one that I had reported earlier.