I have this working locally on OSX.
Firstly build you docker image: https://github.com/spider-gazelle/spider-gazelle/blob/master/Dockerfile <-- this is our base build for microservices.
You want the image to be as small as possible as every arch you add multiplies the size of the image.
So x64 == 20mb, x64 + ARM7 is 40MB etc
You need to enable experimental docker features - you can do this in preferences
Then you can build multi-arch images super easy:
docker buildx build --platform linux/amd64,linux/arm64 -t org/image-name .