I've created a GitHub Action for running commands on multiple platforms. This includes platforms that GitHub Actions don't natively support. It currently supports FreeBSD, OpenBSD and NetBSD. OpenBSD can run on x86-64 and ARM64, the other operating systems run on x86-64.
Some of the features that are supported include:
* Multiple operating system with one single action
* Multiple versions of each operating system
* Allows to use default shell or Bash shell
* Low boot overhead
* Fast execution
* Runs on both macOS and Linux runners
Compared to similar solutions like https://github.com/vmactions/freebsd-vm, the boot time is around a fifth and the full execution time for the same job is around half of freebsd-vm (last time I tried).
The readme contains more information about how it all works under the hood.