Upgrade Debian Linux to Testing

See https://wiki.debian.org/DebianTesting.

Upgrade to testing

Basically (as root):

su -

apt-get update && apt-get upgrade -y
cat <<EOF >/etc/apt/sources.list
deb https://deb.debian.org/debian testing main contrib non-free
deb https://deb.debian.org/debian-security testing/updates main contrib non-free
EOF
apt-get update
apt-get dist-upgrade -y
apt autoremove -y

Then answer the questions.

Add support for new (hardware) ports

If you want to add support for new ports (e.g. RISC-V), do this:

apt-get install -y debian-ports-archive-keyring
cat <<EOF >>/etc/apt/sources.list
deb https://deb.debian.org/debian-ports unstable main
deb https://deb.debian.org/debian-ports unreleased main
deb https://deb.debian.org/debian-ports experimental main
EOF
apt-get update