IIO sensor Proxy service hangs on shutdown
Solution 1:
I had this problem on my HP laptop too: the laptop took way too long to shut down. I didn't uninstall the package just masked the service not to start up on boot:
sudo systemctl mask iio-sensor-proxy.service
then also disable the orientation plugin (which is the only one using the accelerometer):
gsettings set org.gnome.settings-daemon.plugins.orientation active false
You will not have this long shutdown problem any more after your second reboot.