Would this be possible server-side? An option to change the minimum brightness level for nights (different brightness based on the moon phase would be nice) and a pitch-black option for caves.

Would this be possible server-side?

No, skylight is calculated by the client.

Still, could you add this on the client?

Yes, hence not closing it.

I've received an overwhelming number of feature requests over the week and they are filling up the issue tracker and making it difficult to keep track of what is even going on. I've enabled Discussions on the repo as a new location for feature requests. Unfortunately, GitHub has "temporarily" disabled the ability to convert issues to discussions, so I'm closing all feature request issues. However, I'm tracking all the closed issues in a Project board; despite being closed, they're still on my radar on the board. All new feature requests must go to Discussions. Feature requests opened as issues going forward will be closed.