Yes, the Fujifilm X-S20 is compatible with the Sony SF-G Tough 128GB.
Sony SF-G Tough 128GB is V90 class. Meets the floor for: 4K30 (30 MB/s floor); 4K60 (60 MB/s floor). (Peak write 299 MB/s is not evidence of sustained performance; the V90 class rating above decides this.)
“Fujifilm X-S20 specifications: for recording movies at 360Mbps use a SD memory card with Video Speed Class 60 or higher — V90 card exceeds this requirement.”
Last verified:
Compatibility inferred from spec rule (citations above are manufacturer-verified)