As for the last few months, my gnome desktop environment has been messed up(because I went to installing a ton of desktop environments such as kde and unity when I first got Ubuntu a year ago.). My cursor is the cursor from the breeze theme, I still got apps from the MATE and Unity desktop environments on my computer, the UbuntuMATE boot up screen from installing the MATE D.E., Unity login screen(I want to keep this screen though, and if I remember correctly, still have the entire kde plasma D.E. ready to be used, all despite me trying every single tutorial and purge command I could find. I'm desperate for a way to get fix this problem and getting my Ubuntu Gnome desktop to look normal(and yes, I've tried reinstalling the Ubuntu gnome desktop aswell as seeing if installing vanilla gnome works, none do.)
The easiest way to do what you're trying to do is to re-install the operating system and restore your files from backup (you do have backups, right?). From what you've described in your question, it's highly unlikely that every setting and configuration can be returned to default.
However, if you would like to try, then
dconf may get you part of the way there:
$ dconf reset -f /
Very Important: By running this command, Gnome will be reset completely, this includes Gnome-based applications. You may need to re-enter accounts, reconfigure preferences, rebuild playlists (in Rhythmbox), and the like. Do not be surprised if this also removes the login screen that you wish to keep.
If this only gets you part of the way, you can follow it up with a bit more cleanup. In your question you hint that you may have already done this, but here are the steps to get the default Ubuntu desktop environment re-installed:
- Ensure any misconfigured/unconfigured packages are resolved and up to date:
$ sudo dpkg --configure -a
- Ensure any missing dependencies are reinstalled and you're completely up-to-date:
$ sudo apt update $ sudo apt -f install $ sudo apt full-upgrade
- Reinstall the Ubuntu desktop environment and remove any unnecessary cruft:
$ sudo apt install --reinstall ubuntu-desktop $ sudo apt autoremove $ sudo apt clean
If the system is still a giant mess afterwards, grab a Live USB stick and nuke the installation from orbit.