I am using Drupal 10.2.6 and have a layout builder where I need to add a custom block that includes a media library field. The deprecated module "Media Library Theme Reset" worked fine, but when using the recommended replacement module "Layout Builder iFrame Modal", the media library field is not styled correctly.
The media library should be styled correctly, similar to how it appears with the "Media Library Theme Reset" module.
The media library field is not styled correctly and appears broken or unstyled when using the "Layout Builder iFrame Modal" module.
Active
1.3
User interface
Its happens because LB uses frontend theme, not admin theme's CSS and template files.
Maybe this will helps in your case
https://www.drupal.org/project/media_library_theme_reset →
or
https://www.drupal.org/project/layout_builder_admin_theme →