This Mod Is Being Remastered only for 1.21.8 Neoforge and Forge 1.20.1 

1.21.4 doesnt require Geckolib but is Expiremental 

Requires Geckolib for 1.20.1 0.5.5 and any older

This mod allows you to explore new lands, find the exits of the Backrooms levels, and even discover entrances into the Backrooms, located inside small facilities where guards will remain neutral unless provoked by your attempts to enter. You can run from the monsters and creatures lurking in the Backrooms, uncover the infinite mysteries of this eerie world, and explore new levels, with each release adding at least five new, complete, and functional levels to enhance the experience.

Michaels Backrooms is not the "normal" Backrooms or Kane Pixels’ version. Instead, it’s based on a Roblox creator’s idea, which they never finished. With their permission, this mod brings that vision to Minecraft while respecting the essence of the Backrooms.

You’ll still encounter creatures and elements inspired by Backrooms videos and writings, blended seamlessly with this unique interpretation.