apt install fails due to unmet dependencies and held broken packages

Question

I'm attempting to compile synergy from source. But to do so I need to install a number of dependencies. The issue I'm having is that when i go install several of the dependencies I get unmet dependencies errors. One such is for the "qtbase-dev" package. When I run apt install qtbase5-dev I get the following

 some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 qtbase5-dev : Depends: libgl1-mesa-dev but it is not going to be installed or
                        libgl-dev
               Depends: libglu1-mesa-dev but it is not going to be installed or
                        libglu-dev
E: Unable to correct problems, you have held broken packages.

so I started off with . which does nothing. next I attempted to use

sudo apt-get install -f
sudo dpkg --configure -a
sudo apt-get install -f 

which gave no output at all. so it doesn't seem there are actually any held packages next I attempted to clean up

sudo apt-get clean
sudo apt-get autoclean

also looked to remove the held packages

sudo apt-get -u dist-upgrade

I even downloaded synaptic package manage and attempted to install qtbase5-dev from there. and it came back with a similiar error.

Could not apply changes!
Fix broken packages first.

I tried to do that with Synaptic, but it threw more errors.

E: Error, pkgProblemResolver::Resolve generated breaks, this may be caused by held packages.
E: Unable to correct dependencies

here is the out of my /etc/apt/source.

# deb cdrom:[Ubuntu 19.04 _Disco Dingo_ - Release amd64 (20190416)]/ disco 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/ eoan main restricted
# deb-src http://us.archive.ubuntu.com/ubuntu/ disco main restricted

## Major bug fix updates produced after the final release of the
## distribution.
deb http://us.archive.ubuntu.com/ubuntu/ eoan-updates main restricted
# deb-src http://us.archive.ubuntu.com/ubuntu/ disco-updates main restricted

## 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/ eoan universe
# deb-src http://us.archive.ubuntu.com/ubuntu/ disco universe
deb http://us.archive.ubuntu.com/ubuntu/ eoan-updates universe
# deb-src http://us.archive.ubuntu.com/ubuntu/ disco-updates 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/ eoan multiverse
# deb-src http://us.archive.ubuntu.com/ubuntu/ disco multiverse
deb http://us.archive.ubuntu.com/ubuntu/ eoan-updates multiverse
# deb-src http://us.archive.ubuntu.com/ubuntu/ disco-updates 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.
deb http://us.archive.ubuntu.com/ubuntu/ eoan-backports main restricted universe multiverse
# deb-src http://us.archive.ubuntu.com/ubuntu/ disco-backports main restricted universe multiverse

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

deb http://security.ubuntu.com/ubuntu eoan-security main 
# deb-src http://security.ubuntu.com/ubuntu disco-security main restricted
deb http://security.ubuntu.com/ubuntu eoan-security universe
# deb-src http://security.ubuntu.com/ubuntu disco-security universe
deb http://security.ubuntu.com/ubuntu eoan-security multiverse
# deb-src http://security.ubuntu.com/ubuntu disco-security multiverse

# This system was installed using small removable media
# (e.g. netinst, live or single CD). The matching "deb cdrom"
# entries were disabled at the end of the installation process.
# For information about how to configure apt package sources,
# see the sources.list(5) manual.
####deb http://archive.ubuntu.com/ubuntu eoan restricted multiverse main universe
# deb-src http://archive.ubuntu.com/ubuntu eoan universe
# deb-src http://archive.ubuntu.com/ubuntu eoan main universe restricted multiverse

anyone have any suggestions?

The only thing I know that happened recently is an updated from 19.04 to 19.10. as I received a notification that 19.04 would no longer receive updates.

Answer 1

The solution that worked for me is the one below, however, this might not be the case for everyone.

I'm using Ubuntu, I opened the Software & Updates application. In Ubuntu Software, I changed "Download from" to Main Server. Try to change yours to a different server.