I checked my various MA-partner retailer accounts and found that not all of them provided the new 4K version:
Apple TV/iTunes: HD
Vudu: 4K
FandangoNow: 4K
Prime Video: HD (no 4K currently available)
YouTube: Unable to locate
Apple TV/iTunes: HD
Vudu: 4K
FandangoNow: 4K
Prime Video: HD (no 4K currently available)
YouTube: Unable to locate