NCViewer - Open File Browse Dialog-Box not showing

Mill with LinuxCNC on a RPI 4B (works well).

Two support laptops:
 - office Lubuntu doesn't show the drop-down browse dialog box when "Open File" selected,
 - workshop Ubuntu Mate shows the dialog box.

On Lubuntu, I Copy/Paste the file contents and NCViewer displays correctly.
On Ubuntu Mate, the Browse allows file selection then correct display.

Any suggestions on what it is in Lubuntu that prevents the dialog box showing ?
Just hoping someone here has been down this path before !

Keep well,
John.

Opened the discussion on the Lubuntu Discourse Forum.
It appears there may be a driver missing in Lubuntu 22.04 LTS.
The work-around Copy/Paste is bearable, so I will wait to see what happens in the next major release in April next year.

John.