The subsonic Web UI uses frames as if you just proxy subsonic with SSL/TLS termination like you would with any other website you will find the pages does not load. You need to add a directive to your configuration:
add_header X-Frame-Options SAMEORIGIN;
This should also work with madsonic.
Sometimes there the delay between a new certbot release from LetsEncrypt and the time it hits the Ubuntu LaunchPad PPA. However there is not much involved in setting up Ubuntu to use certbot directly from the GitHub source. I tested the following out on Ubuntu 14.04 LTS and 16.04 LTS and it worked without a hitch:
sudo apt-get remove certbot
sudo add-apt-repository --remove ppa:certbot/certbot
sudo git clone https://github.com/certbot/certbot.git
sudo git checkout v0.21.1
sudo ln -s /opt/certbot/certbot-auto /usr/bin/certbot
sudo apt-get autoremove
To update simply go to the repo and `git checkout` the latest version.