While working with VTCompressionSession, I noticed some profiles that were returned by the VTSessionCopySupportedPropertyDictionary but were not documented in header files (other than appearing in the VideoToolbox.tbd file).
Specifically:
kVTProfileLevel_HEVC_Main44410_AutoLevel
kVTProfileLevel_HEVC_Main444_AutoLevel
kVTProfileLevel_H264_High444Predictive_AutoLevel
If I manually define these, they do seem to work OK (macOS/Xcode 26.4). I expect the answer will be that they are undocumented for a reason, but hasn't 4:4:4 encode been a feature for a while?