Starting on February 23, 2023, Actions users of GitHub-hosted larger Linux runners will be able to make use of hardware acceleration for Android testing. Testing on a 4-core machine with hardware acceleration is around 2-3 times faster than not using hardware acceleration and around 2 times faster than using MacOS.

To make use of this on Linux, Actions users will need to add the runner user to the KVM user group

      - name: Enable KVM group perms
        run: |
            echo 'KERNEL=="kvm", GROUP="kvm", MODE="0666", OPTIONS+="static_node=kvm"' | sudo tee /etc/udev/rules.d/99-kvm4all.rules
            sudo udevadm control --reload-rules
            sudo udevadm trigger --name-match=kvm

(Thank you gsauthof for the feedback on this!)

You will then be able to make use of hardware acceleration when making use of Android emulator actions such as reactivecircus/android-emulator-runner.