Yes, the Canon EOS R5 Mark II is compatible with the Samsung PRO Plus 256GB SD.
Canon EOS R5 Mark II's SD slot (Slot 2) accepts Samsung PRO Plus 256GB SD directly. Samsung PRO Plus 256GB SD is V30-rated (equivalent to the UHS Speed Class 3 / U3 floor), clearing only the camera's lowest Long-GOP tier (basic 4K/SRAW at 29.97fps and below, plus FHD) — it never reaches the V60 floor for higher-framerate 4K Long-GOP or the V90 floor for 8K Long-GOP, and no setting or firmware update changes a card's rated speed class. Also, its own card-performance-requirements table shows every RAW, SRAW, and Intra-codec recording mode (XF-HEVC S / XF-AVC S High Quality Intra, Standard Intra, Light Intra) has no SD-card entry at all — those modes are CFexpress-only by design, not just speed-limited. Only Long-GOP (LGOP) compressed modes are SD-eligible.
Limitation
Cannot record 8K Long-GOP (V90), higher-framerate 4K Long-GOP above 29.97fps (V60), or any RAW/SRAW/Intra-codec mode (CFexpress Type B, VPG400 only) on the SD slot. Works for basic 4K/SRAW Long-GOP at 29.97fps and below, and FHD.
“Standard LGOP 29.97 CFexpress 2.0 U3 25.00”
Last verified:
Compatibility inferred from spec rule (citations above are manufacturer-verified)