I have just installed Gimp 2.8.22 Ubuntu 17.10. The problem is when I have already Gimp opened and want to open another image. I go to Open With Other Application and select Gimp, always new instance of Gimp is starting. And I am not even able to drag new file to Gimp. On my other computer once I have Gimp opened and every other file is opened in the same instance on new tab.
I have tried to uninstall Gimp (and even purge), I have tried installing it using Snap or Ubuntu Software center but with the same results.
I am using Single window mode and have just found out there is an area where dropping works (just above tools on the left side of the program) so that part about drag-n-drop not working might be
a feature not a bug. But the other problem still remains. I am at least able to work around that using mouse. Still would be nice if somebody will have a suggestion how to fix that.