Most shaders are specifically hardcoded to apply ambient lighting to the Nether but provide no support for ambient lighting in modded/datapack dimensions. As a result, the Bumblezone dimension tends to be given Overworld lighting by shaders and since Bumblezone has a ceiling, the dimension ends up super dark. An example of the dimension being super dark with Complementary Reimagined shader is shown below:

If you wish to brighten up the dimension, the only two workarounds right now are to disable the shader when you are in Bumblezone dimension or find a way to edit the shader files to apply ambient lighting to the Bumblezone dimension. When Euphoria Patches merges this pull request and releases a new version publically, having that mod on will automatically make Complementary Shaders now give Bumblezone dimension the proper ambient lighting it needs.

Otherwise, you should report the issue to the shader dev to add detection/support for ambient lighting in Bumblezone dimension. (In fact, the dimension type file in Bumblezone already has the ambient light value specified which vanilla Minecraft reads and applies already. Shaders, Optifine, and Iris should update to read and apply this dimension data automatically in my opinion)

Bumblezone in 1.20.1 and newer will ship with an internal resourcepack called "Bumblezone - Shader Emissive".

To activate said resourcepack, go into the game, go to resourcepacks menu, find the resourcepack, and move it over to the right side. Once activated, some of Bumblezone blocks and items will now be emissive when used with some shaders. Example of me moving the resourcepack to the right side column:

Whether the shader or emissive texture mod will actually work with this resourcepack is up to the implementation of those shader/mods. Bumblezone provides both _e emissive files and _s specular files and should work in theory. It also contains proprietary files for compat with certain mods. More details on specific compat with shaders and mods can be found below.

Modpack makers can extract this resourcepack, make changes, and ship it with their modpack. All perfectly fine by me!

When activating the "The Bumblezone - Shader Emissive" resourcepack from Bumblezone while using any variant of Complementary Shaders such as Unbound or Reimagined, you will also need to put on Euphoria Patches mod.

In game, go into Options > Video Settings > Shader Packs > Shader Packs Settings. Once at that spot, now set RP Support: option to be labPBR (RP Required) and this will allow the Complementary Shader with Euphoria Patches to now read Bumblezone's specular files for proper emissive looks.

If you add Supplemental Patches mod alongside Euphoria Patches, you can get colored lighting on Bumblezones blocks by going into Options > Video Settings > Shader Packs > Shader Packs Settings > Configure Euphoria Patches > Popular Settings and then turn Advanced Color Tracing on. Make sure the correct shader is active that was patched by Supplemental Patches. If resourcepack is active, Advanced Color Tracing option is on, patched Complementary Shaders shader is applied, and the colored lighting is still not showing, click Insert key to rebuild the shaderpack in-game.

When activating the "The Bumblezone - Shader Emissive" resourcepack from Bumblezone while using Photon Shaders, you'll need to go into Options > Video Settings > Shader Packs > Shader Packs Settings > Materials. Once at that spot, now set Specular Mapping: option to be on and this will allow the Photon Shader to now read Bumblezone's specular files for proper emissive looks.

Direct compat for Shimmer mod is added in the "The Bumblezone - Shader Emissive" resourcepack. When the resourcepack is activated, it will take effect right away and have Bumblezone blocks give off correct color light around themselves. Some blocks even have bloom applied now!

Direct compat for Colorful Lighting mod is added in the "The Bumblezone - Shader Emissive" resourcepack. When the resourcepack is activated, it will take effect right away and have Bumblezone blocks give off correct color light around themselves. Some blocks also have a color light filter applied too.