Yes, the Samsung PRO Plus 256GB SD is compatible with the Sony Alpha 1.
Samsung PRO Plus 256GB SD is V30 class. Clears: XAVC S HD (100 Mbps, requires U3). Does not meet the floor for: XAVC HS 4K (280 Mbps, requires V60); XAVC S 4K (280 Mbps, requires V60); XAVC HS 8K (520 Mbps, requires V90); XAVC S-I 4K (600 Mbps, requires V90); XAVC S-I HD (222 Mbps, requires V90).
Conditions for compatibility
Compatible for still image shooting and XAVC S HD video at 100Mbps (U3 requirement met). Incompatible with all 4K recording formats — those require SDXC UHS-II (V60 minimum) or CFexpress Type A. Not a viable card for A1 video work.
Limitation
UHS-I card. 4K recording not possible — all 4K formats require at minimum UHS-II V60. Stills and 1080p HD only.
“XAVC S HD 100Mbps CFexpress Type A memory card SDHC/SDXC card (U3 or higher)”
Last verified:
Compatibility inferred from spec rule (citations above are manufacturer-verified)