How often has he been played by actor of Japanese descent at all? There was James Saito in the 1990 movie, though the voice was dubbed over by David McCharen, who... I'm guessing isn't of Japanese heritage.
I'll give BayTurtles this... even though that movie was
hot garbage and its version of the Shredder was maybe the thinnest, lamest version yet, Tohoru Masamune and Brian Tee are both Japanese-American. (Though they originally had the Shredder being the white American Eric Sacks, so I'm not gonna give them
too many points here.)
As for the cartoons, I feel like James Avery, Skottie Ray, and Kevin Michael Richardson were/are all pretty great in their roles. And thankfully avoided the kind of offensive stereotype Leo... vividly described.