Azure has ARM in preview, and AWS has had it for ages. You should be able to create multi-arch builds in CI.
For actually creating multi-arch, I recommend you stay as far away as possible from Docker and use Podman and Buildah. The latter unbundles some of the Docker manifest commands, giving you far more control over how you create multi-arch images. I wasted 4 months on Docker tooling, and got it right in half a week with Podman. This meant switching from DCT (Podman doesn't support this at all) to Cosign, but Cosign is far more sensible than DCT.
There are a rare few containers that you can get away with running on x86.
For actually creating multi-arch, I recommend you stay as far away as possible from Docker and use Podman and Buildah. The latter unbundles some of the Docker manifest commands, giving you far more control over how you create multi-arch images. I wasted 4 months on Docker tooling, and got it right in half a week with Podman. This meant switching from DCT (Podman doesn't support this at all) to Cosign, but Cosign is far more sensible than DCT.
There are a rare few containers that you can get away with running on x86.