Hello Tobi,
thanks for your work from me as well.
Besides this, the site now uses a Letsencrypt SSL certificate and any non-SSL requests get redirected to https://.
This causes a tiny issue on Ubuntu systems that do not have the apt https transport installed.
E: The method driver /usr/lib/apt/methods/https could not be found. N: Is the package apt-transport-https installed?
To make apt-get update work again, one has to manually install apt-transport-https.
apt-get install apt-transport-https