When researching this piece, I was shocked how the world's first adopter of MPC was the 2008 Danish Sugar Beats Auction of all things. Sad to see it's one of the very few, even today in 2023.
FWIW, Apple (and other's) leaked password check algorithm is a big mainstream adoption, but it's hard to count Private Set Instruction when it's a fundamentally easier problem and minimizes the "multi" out of MPC.