but the article itself doesn’t mention what patents AV1 would have broken

The article does mention and links them

Dolby is accusing Snap of infringing upon four of its patents: U.S. Patent No. 10,855,99 “Inter-plane prediction”; U.S. Patent No. 9,924,193 “Picture coding supporting block merging and skip mode”; U.S. Patent No. 9,596,469 “Sample array coding for low-delay”; and U.S. Patent No. 10,404,272 “Entropy encoding and decoding scheme.”