Weird UI/Theme on Ubuntu 20.04 after upgrading from 18.04

I got this weird UI in Ubuntu after upgrading from 18.04. After running into an issue with a login loop I somehow managed to upgrade the distribution but got stuck with this UI/theme.

Does anyone know what the issue is?

You should reset the UI to the default with the following command

dconf reset -f /

As the dconf reset command will reset more than just the Unity, GNOME Shell and MATE desktop you should not run it idly and do make a backup of your existing desktop beforehand, especially if you’ve made extensive customisations and tweaks.

Run dconf dump.

I suppose you need to just to change the theme in gnome-tweaks.

1. Open gnome-tweaks.

2. Navigate to Appearance tab.

3. Choose any theme you like.

You are done! Enjoy!