Every time I download something (linux mint) I get this “Open With” pop-up. Happens in Firefox, Vivaldi, & Chromium with no add-ons. I set Dolphin as my default file manager. I uninstalled Dolphin, and the problem goes away. Basically, it appears Dolphin is trying to Open or Run a file, especially an mp4, instead of just download it to my Downloads folder so I can then go there and open it. It pop ups again even if I hit the Cancel button. After I hit Cancel twice, it will then let me access the Downloads foler.