I had problems in upgrading the system because of mesa unmet dependencies. I've tried to fix it with sudo apt-get --fix-broken install but got the following:
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Correcting dependencies... Done
The following additional packages will be installed:
  libegl-mesa0
The following packages will be upgraded:
  libegl-mesa0
1 upgraded, 0 newly installed, 0 to remove and 1 not upgraded.
1 not fully installed or removed.
Need to get 0 B/148 kB of archives.
After this operation, 0 B of additional disk space will be used.
Do you want to continue? [Y/n] y
(Reading database ... 255254 files and directories currently installed.)
Preparing to unpack .../libegl-mesa0_20.1~git2002021930.0021f7~oibaf~b_amd64.deb ...
Unpacking libegl-mesa0:amd64 (20.1~git2002021930.0021f7~oibaf~b) over (20.0~git2001301930.f09c46~oibaf~b) ...
dpkg: error processing archive /var/cache/apt/archives/libegl-mesa0_20.1~git2002021930.0021f7~oibaf~b_amd64.deb (--unpack):
 trying to overwrite shared '/usr/share/glvnd/egl_vendor.d/50_mesa.json', which is different from other instances of package libegl-mesa0:amd64
Errors were encountered while processing:
 /var/cache/apt/archives/libegl-mesa0_20.1~git2002021930.0021f7~oibaf~b_amd64.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)
At the same time, I'm having an issue with HDMI, which seems to have caused a bizarre glitch in my wallpaper (and sometimes with all GNOME menus):
What could be causing this and how to fix it?

 
     
    