Per Felix Miata:

|Maybe if we saw your sources.list we might be able to suggest a reason. I just

|booted 14.04.5 (with DE KDE only) and updated sources. Subsequently, aptitude

|was unable to locate protonmail*.

# deb cdrom:[Kubuntu 14.04.1 LTS _Trusty Tahr_ - Release amd64 (20120820.1)]/ dists/trusty/main/binary-i386/

# deb cdrom:[Kubuntu 14.04.1 LTS _Trusty Tahr_ - Release amd64 (20120820.1)]/ dists/trusty/restricted/binary-i386/

# deb cdrom:[Kubuntu 14.04.1 LTS _Trusty Tahr_ - Release amd64 (20120820.1)]/ trusty main restricted

# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to

# newer versions of the distribution.

deb http://us.archive.ubuntu.com/ubuntu/ trusty main restricted

deb-src http://us.archive.ubuntu.com/ubuntu/ trusty main restricted

## Major bug fix updates produced after the final release of the

## distribution.

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu

## team. Also, please note that software in universe WILL NOT receive any

## review or updates from the Ubuntu security team.

deb http://us.archive.ubuntu.com/ubuntu/ trusty universe

deb-src http://us.archive.ubuntu.com/ubuntu/ trusty universe

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu

## team, and may not be under a free licence. Please satisfy yourself as to

## your rights to use the software. Also, please note that software in

## multiverse WILL NOT receive any review or updates from the Ubuntu

## security team.

deb http://us.archive.ubuntu.com/ubuntu/ trusty multiverse

deb-src http://us.archive.ubuntu.com/ubuntu/ trusty multiverse

## N.B. software from this repository may not have been tested as

## extensively as that contained in the main release, although it includes

## newer versions of some applications which may provide useful features.

## Also, please note that software in backports WILL NOT receive any review

## or updates from the Ubuntu security team.

## Uncomment the following two lines to add software from Canonical's

## 'partner' repository.

## This software is not part of Ubuntu, but is offered by Canonical and the

## respective vendors as a service to Ubuntu users.

# deb http://archive.canonical.com/ubuntu trusty partner

# deb-src http://archive.canonical.com/ubuntu trusty partner

## This software is not part of Ubuntu, but is offered by third-party

## developers who want to ship their latest software.

deb http://extras.ubuntu.com/ubuntu trusty main

deb-src http://extras.ubuntu.com/ubuntu trusty main

## Trinity Desktop Environment

deb http://mirror.ppa.trinitydesktop.org/trinity/trinity-r14.0.0/ubuntu trusty main

deb-src http://mirror.ppa.trinitydesktop.org/trinity/trinity-r14.0.0/ubuntu trusty main

deb http://mirror.ppa.trinitydesktop.org/trinity/trinity-builddeps-r14.0.0/ubuntu trusty main

deb-src http://mirror.ppa.trinitydesktop.org/trinity/trinity-builddeps-r14.0.0/ubuntu trusty main

## DVD styler

deb http://ppa.launchpad.net/dvdstyler-maintainers/ppa/ubuntu trusty main

deb-src http://ppa.launchpad.net/dvdstyler-maintainers/ppa/ubuntu trusty main

deb http://download.virtualbox.org/virtualbox/debian trusty contrib

deb-src http://download.virtualbox.org/virtualbox/debian trusty contrib

deb http://security.ubuntu.com/ubuntu/ trusty-security main multiverse restricted universe

deb https://deb.torproject.org/torproject.org trusty main

# deb-src https://deb.torproject.org/torproject.org trusty main

|Maybe what you need is to let go of 14.04. What does it have that you can't have

|from 16.04 LTS, Jessie or Stretch, from which you should expect less trouble

|with QT4 or QT5 issues?

when i upgraded from 12.04 LTS to 14.04, i asked here if there were a problem with 16.04 and was told that there was a problem with 16.04 and TDE. has this gotten better? i'd be very happy to make the upgrade!

|What source provides protonmail?

the protonmail service is from protonmail.com, and the protonmail bridge, which is what i'm trying to install, is an encryption/decryption application that allows protonmail to work with a normal mail client. while it has existed for windows and mac for some time, it is in beta for linux, and this is what i'm trying to install. https://protonmail.com/support/knowledge-base/bridge-for-linux/