Updated instructions for configuring the Debian repository could look like:
sudo mkdir -p /etc/apt/keyrings
curl -sS https://download.spotify.com/debian/pubkey_5E3C45D7B312C643.gpg | gpg --dearmor | sudo tee /etc/apt/keyrings/spotify.gpg > /dev/null
echo "deb [arch=amd64 signed-by=/etc/apt/keyrings/spotify.gpg] http://repository.spotify.com stable non-free" | sudo tee /etc/apt/sources.list.d/spotify.list
Note: I also added amd64 as a single architecture, this skips getting the i386 packages index for this repository (i386 Spotify packages look outdated anyway).