Thanks, @deroberts1.
While that’s not AUR, as @cscs said, it seems like a good approach. Instead of switching branches I can just download the nvidia-open-dkms and other related packages directly from a mirror webpage and install with pacman -U as a local file to test it. It should be much easier and safer than switching branches.
I can keep a copy of the working drivers as a backup to restore via tty if something breaks. This approach allows me to test the nvidia-open drivers on the unstable branch and provide feedback on the forum without having to switch to unstable.
Thanks for the suggestion, I’ll try it once the drivers get updates again.