Very strange… So it sounds like you’re using whatever the default file manager is for your desktop, there really isn’t any reason the filesystem type would make things that much slower. Something must be very different about your system to be slowing transfers down that much.

I would use iotop to see how much data is being written, where, and what speeds it’s getting but if you prefer a graphical version of that maybe “system monitor” is available to you in gnome or whatever desktop you use. You’ve probably already tested other drives I guess, maybe try just booting a fresh live USB of something and see if the problem persists there too.