How do I get a list of files in a folder via blueprint, without the need for a plugin?
From my tests, this only works for files in the content folder. Anything outside that will probably need C++.
short answer is stock blueprint has no node for this, which is why every answer ends up in c++. the engine side call is IFileManager FindFiles, the reply above shows the shape of it, and from Blueprint you would need a small function library exposing it.
once you have the paths, images go through ImportFileAsTexture2D and everything else through file helper reads. there is no way around a little c++ or a plugin for the listing part itself, its just not exposed.
you can also try Runtime Directory Watcher, a directory watcher plugin for Unreal Engine that lists and watches folder files straight from Blueprint and loads the images async: Runtime Directory Watcher — Hot-Folder File Events & Async Texture Loader | Fab