I have no expertise in this field and this is what I got just from reading the article without doing any further research.

It seems that a consortium of giant tech companies got together to make a royalty-free video codec called AV1. This included getting legal agreements from a bunch of relevant patent holders that they wouldn't pursue legal action against anyone implementing AV1.

However, due to the U.S. patent office's current policy of issuing patents left and right and letting applicants sort out whether or not their patents are actually unique in court later, lawyers representing Dolby and a couple of other companies that hold some separate video-related patents have smelled money in the water and are trying to sort out whether or not their patents are unique in court.

Dolby: we have a patent that ug let's you do shit to a file so it comes out in another format. We own all formats now and forever!

AV1 has been out almost ten years and Dolby's first case is with Snapchat? Bruh

This wording is wild. They did not say that AV1 uses patented material - they said that AV1 includes some technologies that are in HEVC. Dolby doesn't have a case, and they know it. They are trying to use wording that twists the truth to make it sound like they are in the right.

Patents on software shouldn't exist!

This is my take.

For what it's worth, HEVC seems to have much better hardware support than AV1.

AV1 encodes are also extremely rare when it comes to unofficial content releases.

Til Intel had and dropped support for VVC. Also TIL it's 6 years old I thought it was still in active development.

Oddly specific reference is oddly specific…

Theora is an old and very inefficient codec. VP8, VP9, and now AV1 have succeeded it.

Because Snap has less resources for a long legal fight than Google, Amazon and so on...

The license is royalty free. AOMedia requires it's contributors to contribute royalty free, and AOMedia has worked hard to ensure it doesn't infringe anyone else's IP, but that doesn't stop other companies (some patent trolls) from asserting "You can't do xyz without infringing some obscure patent I own." These companies (like Dolby) target the companies that license AV1, and say "You've infringed my IP. Pay me $x per product that implements AV1, or I will sue you for much greater damages." So AV1 really is licensed royalty free, what we have here is a third party that isn't part of AOMedia (that really liked making money the old way) trying to extract revenue on dubious claims of patent essentiality.

The fun part is that nobody really knows (or cares) whether AV1 is really infringing any IP. They know that the threat of litigation is likely to induce enough people to just pay that the whole charade is worth it. And perhaps ironically, the companies like Dolby want to litigate even less than the companies they are threatening because litigation tends to be a winner take all thing. If they lose, then nobody pays them; not even the companies they bullied into paying. The video codec IP world has operated this way for decades. This is what AOMedia hoped to change. It's Governing Members are some heavy hitters. If they were to defend AV1, they could easily out-muscle players like Dolby. That might happen, but these sorts of things play out over a very long time horizon.

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.”