How can I install a .deb file in Ubuntu-Touch?
While technically you can download a .deb and install it, it's probably not a good idea in many instances.
You need to make the phone read-write (it ships read-only by default) which is not a good idea for most non-developers because the archive used for the phone isn't the full archive, so you may not even find the deb you want. We don't test
apt-get installed scenarios on the phone and if you use
apt-get upgrade, you may install packages which haven't yet been fully tested as part of image based updates.
That said, you can make the phone read-write:-
adb shell sudo mount -o remount,rw /
You can then install a deb using usual tools:-
sudo dpkg -i PackageName.deb
However, you can break the phone and may need to re-flash from scratch if it breaks.