If Cisco Packet Tracer installation on Ubuntu 23.10 (or 24.04) gives you this error

  This package is uninstallable
  Dependency is not satisfiable: libgl1-mesa-glx
  

If your Cisco Packet Tracer installation shows this error

  The following packages have unmet dependencies:
  packettracer: depends: libgl1-mesa-glx but it is not installable
  

Step 1 Download dependecies archives

   Download [[https://github.com/PetrusNoleto/Error-in-install-cisco-packet-tracer-in-ubuntu-23.10-unmet-dependencies/releases/tag/CiscoPacketTracerFixUnmetDependenciesUbuntu23.10 | Here]]

Step 2 install gdebi

  sudo apt install gdebi
  

Step 3 install dependecies

go to the Downloads page, in terminal

   cd /home/yourUser/Downloads
   

install dependencies

   sudo gdebi ./libegl1-mesa_23.0.4-0ubuntu1.22.04.1_amd64.deb 
   sudo gdebi ./libgl1-mesa-glx_23.0.4-0ubuntu1.22.04.1_amd64.deb
   

Step 4 install CiscoPacketTracer

   sudo gdebi ./Packet_Tracer821_amd64_signed.deb

or

   sudo gdebi ./YOURPACKETTRACKERARCHIVE.deb

Credits to the original owner PetrusNoleto