OpenZFS on OS X

Has development on intel stopped, or why are the latest builds available only for arm64?

Any chance that these will become universal builds, rather than CPU specific ones?

You want the Catalina build on this post – it contains the Intel build.

Lundman hasn't said why the Intel build is Catalina as a minimum and the ARM-64 one is Sonoma as the minimum, there must be some backwards compatibility issue with the ARM-64 build. But unless stated otherwise builds should be forward compatible so the Catalina build will work on Sonoma and Sequoia as well. That said, keep in mind that Sequoia should be considered under testing until Lundman posts a final release, which is we get builds for every OS and architecture (though IMO it's not needed to do each one specifically).

Lundman is the only one working on OpenZFS for OS X so we're at the mercy of their schedule (when they have free time enough and the desire to work on it), so patience is required.

I don't think ARM CPUs were around when Catalina was released. Wasn't Sonoma the first OS that supported ARM64?