LuckyBackup superuser does not start on X11

In Linux Mint MATE 20 (new install), I installed LuckyBackup package. I can start it from the Mint menu, as usual user. But when I start it from the Mint menu as super user (it's better to do that when backuping), Linux asks me my password and after that, tries to start LuckyBackup (the mouse cursor becomes a rotating wheel). But LuckyBackup doesn't start. After 10-20 seconds, the mouse cursor becomes as usual.

LuckyBackup version is 0.5.0.
On http://luckybackup.sourceforge.net/bugs.html, this bug is marked as solved with this version but it's not the case with the command line that is used actually in the Linux Mint menu :
/usr/sbin/sudo -H luckybackup

In a terminal :

$ pkexec "/usr/bin/luckybackup"
qt.qpa.xcb: could not connect to display
qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.

Available platform plugins are: eglfs, linuxfb, minimal, minimalegl, offscreen, vnc, xcb.

Abandon (core dumped)

I tried the other command line proposed in http://luckybackup.sourceforge.net/bugs.html and it works in a terminal but not in the menu : /usr/bin/sudo -H luckybackup

For information : https://github.com/linuxmint/linuxmint/issues/277