There are 2 repositories under lua-gui topic.
Lua bindings for FLTK
Lua Widget Toolkit: implement cross platform GUI widgets in pure Lua on top of LPugl or LÖVE 2D game engine
A minimal Lua-API for building GUIs using Cairo or OpenGL (see: https://github.com/osch/lua-lpugl#lpugl)
Lua + GTK + Granite + Flatpak
A simple filepicker for LOVE's imgui module