EDIT: I see there is already a workflow, but it doesn't build for arm64 or trixie, nor does it publish a github release with built packages. I'll see if I can fix that.
github actions/workflows support both amd64 and arm64, and are free to use for public repositories. I'll see if I can cook up something to build the packages using that, and pull-request it if it works. it could also potentially replace the buildbot altogether - I'm not sure if that's a good idea or not.
that said, I'm a bit short on time at the moment, so don't expect the PR tomorrow.
