I don't know how they are tracking now, but this comapny made some waves with their seaweed approach back in 2021: https://www.scoop.co.nz/stories/BU2112/S00513/ch4-aotearoa-opens-auckland-office-and-expands-team-after-announcing-further-investment-by-sir-stephen-tindall.htm
Basically, they feed a red seaweed to dairy cows and the cows fart less. From memory it was something in the seaweed that prevented a specific type of bacteria that produces the most methane. Back in 2021, there wasn't a lot of research around long-term health for the cattle, or how it affected the milk product, but it was a very promising approach.
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