You have wrong repositories in your system, see details below:
Qt4 from rock-core does not provide packages for 18.04 LTS, so should be removed by
sudo add-apt-repository -r ppa:rock-core/qt4
Ubuntu 18.04 LTS (bionic) is actual release, so its packages are located in archive, not old-releases. You can fix this problem by using command below:
sudo sed -i "s/mx.old-releases/archive/g" /etc/apt/sources.list /etc/apt/sources.list.d/*.list
sudo sed -i "s/old-releases/archive/g" /etc/apt/sources.list /etc/apt/sources.list.d/*.list
For sure re-add correct repositories to the system
sudo add-apt-repository "deb http://archive.ubuntu.com/ubuntu bionic main restricted universe multiverse"
sudo add-apt-repository "deb http://archive.ubuntu.com/ubuntu bionic-updates main restricted universe multiverse"
sudo add-apt-repository "deb http://archive.ubuntu.com/ubuntu bionic-security main restricted universe multiverse"
sudo add-apt-repository "deb http://archive.ubuntu.com/ubuntu bionic-backports main restricted universe multiverse"
Ubuntu 18.04 LTS is supported release, so ESM is not needed for it, remove such repositories by
sudo rm /etc/apt/preferences.d/ubuntu-esm-infra
sudo rm /etc/apt/sources.list.d/ubuntu-esm-infra.list
Then update package lists as usual, install upgrades with new dependencies and install GRC from already correctly chosen GnuRadio's PPA:
sudo apt-get update
sudo apt-get dist-upgrade
sudo apt-get install gnuradio
To get 3.8 version you have to purge the master branch repository by
sudo apt-get install ppa-purge
sudo ppa-purge ppa:gnuradio/gnuradio-master
And also releases PPA by
sudo ppa-purge ppa:gnuradio/gnuradio-releases
To stay only with gnuradio-releases-3.8 PPA.