Ubuntu upgrade leads unmet dependencies

so after upgrading from Ubuntu 18.04 to 20.04 my system settings were gone. Trying to fix it (by installing gnome-control-center) lead to some unmet dependencies which I tried to fix (and that didn’t work). I changed the setting I needed directly, but upon restarting the laptop today I got an error message:

iwlwifi: 0000:02:00.0: BIOS contains WGDS but no WRDS

In recovery mode I tried to install ubuntu-desktop (not reinstall, it is not currently installed to my surprise), which didn’t work and gives the following error:

ubuntu-desktop: Depends: gdm3 but it it not going to be installed
Depends: gnome-control-center but it it not going to be installed
Depends: gnome-shell but it it not going to be installed
Depends: gnome-shell-extension-appindicator but it it not going to be installed
Depends: gnome-shell-extension-desktop-icons but it it not going to be installed
Depends: gnome-shell-extension-ubuntu-dock but it it not going to be installed
Depends: ubuntu-desktop-minimal but it it not going to be installed
Depends: ubuntu-release-upgrader-gtk but it it not going to be installed
Depends: ubuntu-session but it it not going to be installed
Depends: update-manager but it it not going to be installed
Depends: xorg but it it not going to be installed
Depends: yelp but it it not going to be installed
Depends: zenity but it it not going to be installed
Recommends: cheese but it it not going to be installed
Recommends: gnome-calendar but it it not going to be installed
Recommends: gnome-getting-started-docs but it it not going to be installed
Recommends: gnome-initial-setup but it it not going to be installed
Recommends: gnome-todo but it it not going to be installed
Recommends: nautilus-share but it it not going to be installed
Recommends: shotwell but it it not going to be installed
Recommends: totem but it it not going to be installed
Recommends: ubuntu-docs but it it not going to be installed
E: Unable to correct problems, you have held broken packages

I have checked for broken packages with dpkg --get-selections | grep hold, which yields no result.

I have tried sudo dpkg --configure -a,
sudo aptitude install ubuntu desktop,
sudo apt-get -f install,
and sudo apt-get update, neither of which changes anything.

If I were home I would just reinstall Ubuntu, but I am not so I don’t have the option to do that.

Is there a way to resolve the dependency issue? Recursively trying to manually install the Depends: … packages seems like it might not be a fruitful endeavor.

Edit:
Running grep -r deb /etc/apt/sources.list /etc/apt/sources.list.d gives:

/etc/apt/sources.list:# cdrom:[Ubuntu 18.04.3 LTS _Bionic Beaver_ - Release amd64 (20190805)] Biopic main restricted
/etc/apt/sources.list: deb http://de.archive.ubuntu.com/ubuntu/ focal main restricted 
/etc/apt/sources.list:# deb-src http://de.archive.ubuntu.com/ubuntu/ bionic main restricted
/etc/apt/sources.list: deb http://de.archive.ubuntu.com/ubuntu/ focal-updates main restricted
/etc/apt/sources.list:# deb-src http://de.archive.ubuntu.com/ubuntu/ bionic-updates main restricted
/etc/apt/sources.list: deb http://de.archive.ubuntu.com/ubuntu/ focal universe
/etc/apt/sources.list:# deb-src http://de.archive.ubuntu.com/ubuntu/ bionic universe
/etc/apt/sources.list: deb http://de.archive.ubuntu.com/ubuntu/ focal-updates universe
/etc/apt/sources.list:# deb-src http://de.archive.ubuntu.com/ubuntu/ bionic-updates universe
/etc/apt/sources.list: deb http://de.archive.ubuntu.com/ubuntu/ focal multiverse 
/etc/apt/sources.list: # deb-src http://de.archive.ubuntu.com/ubuntu/ bionic multiverse
/etc/apt/sources.list: deb http://de.archive.ubuntu.com/ubuntu/ focal-updates multiverse
/etc/apt/sources.list: # deb-src http://de.archive.ubuntu.com/ubuntu/ bionic-updates multiverse
/etc/apt/sources.list: deb http://de.archive.ubuntu.com/ubuntu/ focal-backports main restricted universe multiverse
/etc/apt/sources.list: # deb-src http://de.archive.ubuntu.com/ubuntu/ bionic-backports main restricted universe multiverse
/etc/apt/sources.list: # deb http://archive.canonical.com/ubuntu bionic partner
/etc/apt/sources.list: #deb-src http://archive.canonical.com/ubuntu bionic partner
/etc/apt/sources.list: deb http://security.ubuntu.com/ubuntu focal-security main restricted
/etc/apt/sources.list: #deb-src http://security.ubuntu.com/ubuntu bionic-security main restricted
/etc/apt/sources.list: deb http://security.ubuntu.com/ubuntu focal-security universe
/etc/apt/sources.list:# deb-src http://security.ubuntu.com/ubuntu bionic-security universe
/etc/apt/sources.list: deb http://security.ubuntu.com/ubuntu focal-security multiverse
/etc/apt/sources.list: # deb arc http://security.ubuntu.com/ubuntu bionic-security multiverse
/etc/apt/sources.list.d/google.chrome.list.save: deb [arch=amd64] http://dl.google.com/linux/chrome/deb/ stable main
/etc/apt/sources.list.d/oibaf-ubuntu-graphics-drivers-bionic.list: # deb http://ppa.launchpad.net/oibaf/graphics-drivers/ubuntu focal main # disabled on upgrade to focal
/etc/apt/sources.list.d/oibaf-ubuntu-graphics-drivers-bionic.list: # deb-src http://ppa.launchpad.net/oibaf/graphics-drivers/ubuntu bionic main 
/etc/apt/sources.list.d/oibaf-ubuntu-graphics-drivers-bionic.list.distUpgrade: deb http://ppa.launchpad.net/oibaf/graphics-drivers/ubuntu bionic main 
/etc/apt/sources.list.d/oibaf-ubuntu-graphics-drivers-bionic.list.distUpgrade:# deb-src http://ppa.launchpad.net/oibaf/graphics-drivers/ubuntu bionic main 
/etc/apt/sources.list.d/google-chrome.list.distUpgrade: deb [arch=amd64] http://dl.google.com/linux/chrome/deb/ stable main
/etc/apt/sources.list.d/google-chrome.list: deb [arch=amd64] http://dl.google.com/linux/chrome/deb/ stable main

Thanks if anyone can help!

sudo add-apt-repository ppa:oibaf/graphics-drivers
sudo apt update
sudo apt upgrade
sudo apt-get install ubuntu-desktop