→ https://askubuntu.com/questions/1035209/how-to-turn-off-screen-rotation-in-ubuntu-18-04-lts/1059678#1059678

sudo systemctl stop iio-sensor-proxy.service
sudo systemctl disable iio-sensor-proxy.service

sudo apt-get remove iio-sensor-proxy

gsettings set org.gnome.settings-daemon.plugins.orientation active false