When playing with this mod, this liquid does not pour out, can this problem be related to others mods, and if you can, please tell me which of these:

architectury
autoreglib
Botania
Caelus forge
Cloth config
CTM-MC
Curios forge
Geckolib forge
Immersive engineering
Iron chest
Journeymap
Obseverlib
Occultism
Origins forge
REI
Twilight Forest
Useful backpacks
Wthit

Assuming you mean placing a bucket down doesn't flow, yes that's another mod causing that. Liquid Starlight should flow like water, only faster.

Best bet would be to remove half of the mods at a time (outside of dependencies) and keep reducing the mod selection by half until you've narrowed down which mod it is causing the issue.

The mod causing the issue is REI. You can replace it with JEI and it should work fine. I do not know what causes these mods to conflict, but other mods' buckets have this issue with REI as well.