Yes, the Canon EOS R50 is compatible with the Samsung PRO Plus 256GB SD.
Samsung PRO Plus 256GB SD is V30 class. Meets the floor for: 4K30 (30 MB/s floor). (Peak write 90 MB/s is not evidence of sustained performance; the V30 class rating above decides this.)
“Canon EOS R50 Reference Guide: recording media is SD/SDHC/SDXC with UHS-I support; 4K UHD IPB at 120 Mbps recorded on single UHS-I slot.”
Last verified:
Compatibility inferred from spec rule (citations above are manufacturer-verified)