[NEED HELP] can't join any server in the list

Hello to everybody.  
I can't join any server on the list when I click the appropriate button whenever the server is crowded or empty ('join' ...). Sometimes a black screen appears and after one minute, the server list windows pops up again.
I managed to get online only once ! But 99.99 % of the time, it fails.
I have no problem to play online with UT4.
My rig: 
ubuntu 18.04.1, kernel 4.18.8. AMD Ryzen 1700 and fury R9 X.
I tried to find logs on xonotic, to launch xonotic from the console to watch events but there is no feedback when I try to join a server. 
I've no local firewall, nor on the 4G router.
Thanks for any tips (logs localization and/or activation, etc)

Since you only connected once, I'm assuming you don't have too much customization done yet. The easiest way is probably just restart from scratch. The following steps will reset most things to your default (but will preserve your identity).
First back your current setup:

Code:

$ mv ~/.xonotic ~/.xonotic.backup

Then create a new directory but port your old identity:

Code:

$ mkdir ~/.xonotic
$ cp -p ~/.xonotic.backup/key_* ~/.xonotic

Now restart Xonotic.
I'm hoping this will resolve your problem, but if it doesn't, restore to your original setup by:

Code:

$ rm -rf ~/.xonotic
$ mv ~/.xonotic.backup ~/.xonotic

and we can dig deeper.

Since you only connected once, I'm assuming you don't have too much customization done yet. The easiest way is probably just restart from scratch. The following steps will reset most things to your default (but will preserve your identity).
First back your current setup:

Code:

$ mv ~/.xonotic ~/.xonotic.backup

Then create a new directory but port your old identity:

Code:

$ mkdir ~/.xonotic
$ cp -p ~/.xonotic.backup/key_* ~/.xonotic

Now restart Xonotic.
I'm hoping this will resolve your problem, but if it doesn't, restore to your original setup by:

Code:

$ rm -rf ~/.xonotic
$ mv ~/.xonotic.backup ~/.xonotic

and we can dig deeper.

Hi buddy

sorry for the late reply. Back from Mauritius after sun bathes ;-)...
I will try the trick and report asap.