Yes, the Canon EOS R3 works with the Sony Tough G 128GB CFexpress Type B — with conditions (see below).
Canon EOS R3 Slot 1 accepts CFexpress Type B and requires a card rated 400 MB/s sustained for its 6K RAW and 4K 120fps HFR modes. Sony Tough G 128GB CFexpress Type B's VPG certification could not be confirmed -- Sony's own spec page 403s, and independent research indicates only the larger CEB-G960T/CEB-G1920T variants are VPG400-certified, not this 128GB card. Peak write of 1480 MB/s is not evidence it meets the 400 MB/s sustained floor -- verify this card's real sustained write speed or VPG rating before relying on it for 6K RAW or 4K 120fps HFR.
Conditions for compatibility
Fits Slot 1 (CFexpress Type B). Sony Tough G 128GB's VPG rating is not confirmed in the DB -- verify VPG400 or an equivalent 400 MB/s sustained write speed before using for 6K RAW or 4K 120fps HFR.
“CFexpress memory card Type B VPG400 support SD memory card Compatible with UHS-II”
Last verified:
Compatibility inferred from spec rule (citations above are manufacturer-verified)