Yes, the Canon EOS R5 Mark II is compatible with the Lexar Professional 2000x 256GB SD.
Canon EOS R5 Mark II's SD slot (Slot 2) accepts Lexar Professional 2000x 256GB SD directly. Lexar Professional 2000x 256GB SD is V90-rated, clearing the SD slot's highest reachable Long-GOP floor (8K LGOP at V90) — every Long-GOP mode this camera offers on the SD slot works. But 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.
Conditions for compatibility
4K30 via SD slot supported. 4K60 and above requires CFexpress Type B in primary slot.
Limitation
Cannot record any RAW, SRAW, or Intra-codec mode on the SD slot (8K RAW, XF-HEVC S/XF-AVC S Intra) — those are CFexpress Type B only, VPG400 required. Works for every Long-GOP mode including 8K LGOP.
“Standard LGOP 29.97 CFexpress 2.0 V90 25.00 24.00 23.98”
Last verified:
Compatibility inferred from spec rule (citations above are manufacturer-verified)