Yes, the Canon EOS R5 Mark II is compatible with the Lexar Professional 2000x 128GB SD UHS-II.
Canon EOS R5 Mark II's SD slot (Slot 2) accepts Lexar Professional 2000x 128GB SD UHS-II directly. Lexar Professional 2000x 128GB SD UHS-II 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.
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)