Crash of geometry/geoviewer on Kubuntu 20.04 LTS

Reinstallation of the latest version of Flair + Fluka on new laptop with Kubuntu 20.04, Fluka 4.1.1 and Flair 3.1.8
No problems installing Fluka and Flair, no problems with GCC and GFORTRAN 9.3.0, or Python 3.8.5.
All installed with apparent success, no error messages.
flair opens without problems, check performed successfully, latest version OK. All menus work, Flair, Input, Run, Plot, flair run with Basic.
If you press the Geometry key, the Flair window will crash with the following message:
X Error of failed request: BadLength (poly request too large or internal Xlib length error)
Major opcode of failed request: 139 (RENDER)
Minor opcode of failed request: 20 (RenderAddGlyphs)
Serial number of failed request: 81727
Current serial number in output stream: 81952

Thanks to the help of Vassilis the problem was fixed. It was not a geoviewer problem but an X11 issue on kubuntu 20.04.
the problem was solved with:

sudo apt purge fonts-known-color-emoji

What emojis have to do with geoviewer is not known, geoviewer do not use emoji but now flair + fluka run smoothly.

Angelo Maggiora
INFN Turin

PS this is not a request for help but an information in case someone else finds the same problem


Thank you Angelo for reporting