No, the Canon EOS R3 is not compatible with the ProGrade Digital CFexpress Type A 120GB.
Canon EOS R3 Slot 1 accepts only CFexpress Type B. ProGrade Digital CFexpress Type A is physically incompatible with the R3's Type B slot.
What works instead
See all compatible camera for the Canon EOS R3 →“When recording movies, use a CFexpress card that supports VPG400”
Last verified:
Confidence: inferred