I’ve experienced this problem on my Elementary OS setup in the middle of setting things up my working environment
sudo add-apt-repository <some repository> Command add-apt-repository not found
Have you encountered this kind of problem? You want to add a ppa repository but the following command is not recognized by your linux distro. Try the following fix. This might work for you if you are using debian-based operating system including ubuntu.
sudo apt install software-properties-common
I’m using Elementary OS, and so far, this solution worked for me. Hope this works on your Linux distro 🙂