You can also use Bubblewrap, but getting it up and running requires a lot more fiddling around. For example, this is what I use to isolate Zoom from the rest of my system: https://gitlab.com/yorickpeterse/dotfiles/-/blob/0a0492c78b6...

In my case I'm using Bubblewrap because Firejail was only used for Zoom, and this felt a bit of a waste considering Bubblewrap was already installed.