There's a closed pull request on the void-packages repository

Update acpid handler
https://github.com/void-linux/void-packages/pull/25909

Description:
The first 5 commits are various cleanups that should have no functional change. The last commit adds support for increasing and decreasing the backlight brightness. If preferred I can rebase that out and keep it as a local modification. (I have another local modification for the volume keys that I don't think can be made generic and upstreamed anyway.)