I am running a new install of Ubuntu 18.10 on Wayland. I recently installed the Polo file manager and it has made itself the default file manager. However I prefer Nautilus to be the default when I plug in a USB-Stick.
How can I make Nautilus the default application for my USB-sticks again?
The problem was indeed the Polo file manager and that is also the solution. In the Polo file manager, I went to Setup and then General and then you can choose underFile Manager either Files, Polo or Disc Usage Analyser.
Sorry for posting such a question but I was genuinely puzzled and would still like to know if there is a relatively simple way to set the default file manager in Ubuntu.