Notepadqq doesn't ask to retry as root, gksu doesn't work

I want to open config files in Notepadqq. When I try to do this normally, I get an error dialog with message "Permission denied" and options Ignore, Abort and Retry. Supposedly if gksu is detected Notepadqq will offer the option to retry as root, but it doesn't for me even though though I have gksu installed. Running gksu notepadqq in a terminal brings up the enter password dialog, and when I enter my password it disappears and nothing else happens. The terminal command ends with no output and Nqq doesn't launch. gksudo notepadqq has the same effect. sudo notepadqq nags about how you're not supposed to use sudo, but sudo notepadqq --allow-root succeeds in running it as root, with a different graphical theme. pkexec notepadqq gives: qt.qpa.screen: QXcbConnection: Could not connect to display Could not connect to any X display. How do I get edit files as root with Notepadqq?