• Install gnome-session and some components:

  sudo apt install gnome-session gnome-tweaks chrome-gnome-shell

• Restore the default login screen style:

  sudo update-alternatives --config gdm3.css

Select /usr/share/gnome-shell/theme/gnome-shell.css

Log out from your PC and switch the session to GNOME by clicking the gear icon

Go to extensions.gnome.org and install the User Themes extension

Go to Tweaks and set themes, icons, etc in Adwaita

Removing snapd

Snaps are a self-contained package technology that allows software to be installed without worrying about incompatible libraries. The downside is that apps are bigger in size and the startup may be slower.

sudo rm -rf /var/cache/snapd/

sudo apt autoremove --purge snapd gnome-software-plugin-snap

rm -rf ~/snap

You may have to run apt install gnome-calculator gnome-system-monitor to get back some default applications that were initially shipped as snaps.