Disable lightbox on single post featured images + Remove featured per category

Hi there,

I’m trying to disable the lightbox on single post featured images with no luck

I’ve tried the css on these forum posts and its not working:

https://kriesi.at/support/topic/how-to-remove-lightbox-from-featured-image/

This does not remove the lightbox?:

#top.single-post .big-preview.single-big a,
#top.single-post .small-preview {
pointer-events: none;
cursor: default;
}

Also, https://kriesi.at/support/topic/featured-image-with-or-withouk-a-lightbox-effect/

This does not remove the lightbox?:

.big-preview.single-big { pointer-events: none; }

Plus, I’m trying to remove / disable some single post featured images based on post category. I have tried several css with no luck, example:

.category-15 .post-loop-1 .big-preview {
display: none;
}

.category-15 .single div.big-preview.single-big, .single .small-preview {
display: none !important;
}

Please help me with the correct css – much appreciated!

Thanks very much!