Yes, the Canon EOS R50 is compatible with the Lexar Professional 1667x 64GB SD.
Lexar Professional 1667x 64GB SD is V60 class. Meets the floor for: 4K30 (30 MB/s floor). (Peak write 120 MB/s is not evidence of sustained performance; the V60 class rating above decides this.)
“Canon EOS R50 Compatible Cards: SD/SDHC/SDXC memory cards — UHS-I cards supported; UHS-II cards operate in backward-compatible UHS-I mode per Canon online manual.”
Last verified:
Compatibility inferred from spec rule (citations above are manufacturer-verified)