Ubuntu 20.10 has a polished GNOME theme. It's called Yaru and it comes in light/dark versions for gtk2 & gtk3. It bundles an icon & cursor theme which is based on the Suru icon theme.

To install the Yaru theme properly on openSUSE, we need to compile a few files first and to do so we require a few tools.

sudo zypper in git meson ninja glib2-devel sassc

Once we have the tools installed, we clone the Yaru theme project from GitHub.

git clone https://github.com/ubuntu/yaru.git

Next, we build the theme & install it.

cd yaru
meson "build" --prefix=/usr
sudo ninja -C "build" install

The Yaru theme will then be available for selection from the GNOME Tweaks configuration tool.

GNOME Tweaks
GNOME Tweaks

Select Yaru as the Applications, Cursor and Icon themes. You may also select it as the sound theme as well if you want.

Lastly, enable the Dash to Dock extension for GNOME and you should have a polished desktop.