No Apple user here, but for my knowledge this comes through Apple changing something and unfortunately there is no fix so far.
But there is a workaround which at least works for the Krita 5 versions, you can install the plugin Buli Commander which is a file manager for Krita and has some options how to show previews.
Here you’ll find the last working version, the plugin is no longer maintained but functional:
and here a description of its options and abilities:
Hello @BriJo1103, and welcome to the forum!