Yes, the Canon EOS R5 Mark II is compatible with the Samsung PRO Plus 256GB SD.
Samsung PRO Plus is UHS-I, rated UHS Speed Class 3 (U3) per Samsung's own spec page. Canon R5 Mark II's codec table requires only U3 on the SD slot for Standard LGOP 4K-UHD Fine recording; higher-bitrate Intra/V60/V90 modes require CFexpress. Card meets the SD-slot floor for that mode -- corrected 2026-06-21, previous verdict ("UHS-I cards will not record 4K at any framerate") was never sourced and contradicted Canon's own manual.
Limitation
Cannot record 4K60 (Video Speed Class V60), 4K120 (V90), or any CFexpress-only Intra/RAW mode on the SD slot -- this card is U3/V30. Works for 4K-UHD Fine Standard LGOP (29.97/25/24/23.98fps) and standard modes on the SD slot.
“Standard LGOP 29.97 CFexpress 2.0 U3 25.00 24.00 23.98”
Last verified:
Compatibility inferred from spec rule (citations above are manufacturer-verified)