Allow user to upload multiple files or images at once?

Hi, is there currently any way to allow a user to upload multiple files or images at once?
I have a customer asking for this but can't seem to find a way to accomplish it.

I've seen this topic mentioned a couple times on this forum, but many answers are over a year old and non-definitive. Is anyone able to tell me what is currently possible in this regard?
I'm curious about the possibilities in every GUI.

Thanks in advance.