If you feel like running arbitrary code downloaded over the internet (pypi doesn't support gpg signatures anymore), mat2 is available on pypi, and can be installed like this:
pip3 install mat2
When bubblewrap is installed, mat2 uses it to sandbox any external processes it invokes.
Thanks to kpcyrd, there is an package available on Arch linux's AUR.
There is a package available in Debian and you can install mat2 with:
apt install mat2
Thanks to atenart, there is a package available on Fedora's copr.
First you need to enable mat2's copr:
dnf -y copr enable atenart/mat2
Then you can install mat2:
dnf -y install mat2
mat2 is available in the torbrowser overlay.
mat2 is available on homebrew:
brew install mat2
mat2 is available on MacPorts:
port install mat2