Hi,
UIkit does not have a built-in gallery with thumbnail navigation on one line.
Could you please clarify your requirements?
Do you need the thumbnails to be displayed in a single row with a horizontal slider (scrolling left and right), or is it sufficient to show them below the main image, wrapping onto multiple lines if there are many thumbnails?
Alternatively, do you need thumbnails at all, or would a simple image slider with left/right navigation arrows be enough?
Here is what we can do:

When you click on thumbnail, then big image changes. Without popup window.
Is it ok for you?