Gentoo unsupported
tfoerste@t44 ~/devel/ooni-probe $ ./setup-dependencies.sh -u It appears that you are using an unsupported OS - please tell us by filing a bug: https://trac.torproject.org/projects/tor/newticket
This might help :
tfoerste@t44 ~/devel/ooni-probe $ cat /etc/gentoo-release Gentoo Base System release 2.2