firstly. you just need to follow the instruction in below link to install the webex

• https://help.webex.com/en-us/article/9vstcdb/Webex-App-for-Linux#Cisco_Reference.dita_86ea12dd-8b6c-4c57-bcdf-63878239b931

if you miss the lib of libgl1-mesa-glx . you can follow the link below - https://packages.ubuntu.com/lunar/amd64/libgl1-mesa-glx/download - for short just need to add below line to /etc/apt/source and - run sudo apt update

deb http://cz.archive.ubuntu.com/ubuntu lunar main universe