When software is not in the repo’s, You will have to use other options. Snap, Flatpak, and appimages are all goof. However, when using Debian/Ubuntu based distros there is a option witch in my opinion is better than all of these. Deb files. Deb files are files that allow you to install the files on your system. Most applications will have their .deb file online. However, they can be difficult to install. I am going to go over the best way to use .deb files to install software on your system.
sudo apt install ./nameofdebfile.deb
#dpkg -i /path/to/deb/file && apt --fix-missing install
Don’t even @ me about it. You all know it’s true.
Only because the above is not well known.