User-agent:
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0
one of the particular strengths of the Ubuntu Touch UI is that you can
see what apps are running and close the things you don't want. This is
considerably easier on Ubuntu than it is on Android (long press of the
button on the right that nobody knows what it does, then see your list
of apps and wonder how to close them, then give up) On Ubuntu it is go
to the switcher and swipe up or down to kill things. This could be
enhanced, to renice the applications. Drag them up a bit to make them
faster, drag down to slow them to a crawl, swipe all the way down to
kill nicely and swipe up to nuke it from orbit with a kill -9 (it is the
only way to be sure)