Basically you just need to edit the service call used in the script and the service data, so it will envoke spotcast and the Spotify URI instead of radio streams.
spotify:
alias: Start Spotify
sequence:
- service: spotcast.start
data_template:
entity_id: >
{% if is_state("input_select.google_cast", "Sony") %} media_player.sony_cast
{% elif is_state("input_select.google_cast", "Badkamer") %} media_player.badkamer_cast
{% elif is_state("input_select.google_cast", "Sony Stereo") %} media_player.sony_stereo_cast
{% elif is_state("input_select.google_cast", "Multispeakers") %} media_player.multispeakers_cast
{% elif is_state("input_select.google_cast", "Party Speakers") %} media_player.party_speakers
{% elif is_state("input_select.google_cast", "Super Groep") %} media_player.super_groep
{% endif %}
uri: >
{% if is_state("input_select.spotify_playlist", "Global Top 50") %} spotify:playlist:37i9dQZEVXbMDoHDwVN2tF
{% elif is_state("input_select.spotify_playlist", "Today's Top Hits") %} spotify:playlist:37i9dQZEVXbMDoHDwVN2tF
{% elif is_state("input_select.spotify_playlist", "New Music Friday") %} spotify:playlist:37i9dQZF1DX4JAvHpjipBk
{% elif is_state("input_select.spotify_playlist", "Discover Weekly") %} spotify:playlist:37i9dQZEVXcQorVlmdOh35
{% elif is_state("input_select.spotify_playlist", "Neef") %} spotify:playlist:0hbQY0xakFZ0o5Xf30rlph
{% elif is_state("input_select.spotify_playlist", "Omelette du Frommage") %} spotify:playlist:3w16ohVvJwiYZ8N1Kz6tIz
{% elif is_state("input_select.spotify_playlist", "Fissa") %} spotify:playlist:5WZ951CGTTuOeay4c7jMsb
{% elif is_state("input_select.spotify_playlist", "Baila Reggaeton") %} spotify:playlist:37i9dQZF1DWY7IeIP1cdjF
{% elif is_state("input_select.spotify_playlist", "Golden Era Music") %} spotify:playlist:1X8CLmPyo2dBLXgmOotqGb
{% elif is_state("input_select.spotify_playlist", "Rock") %} spotify:playlist:5BI3eXjUNc7CmDTRQo8Eh2
{% elif is_state("input_select.spotify_playlist", "Golden Oldies") %} spotify:playlist:3oqXop9kNZ1JCbJTyk9sJs
{% elif is_state("input_select.spotify_playlist", "Lo-Fi Hip-Hop") %} spotify:playlist:37i9dQZF1DWWQRwui0ExPn
{% elif is_state("input_select.spotify_playlist", "Supalonely Radio") %} spotify:playlist:37i9dQZF1E8BaEV2PtTgL1
{% elif is_state("input_select.spotify_playlist", "Morning Dew Radio") %} spotify:playlist:37i9dQZF1E8AvabLLYZIuG
{% elif is_state("input_select.spotify_playlist", "Winter Acoustic") %} spotify:playlist:4LFjFTv8HmijBmqVwIyxnb
{% elif is_state("input_select.spotify_playlist", "Koffiehuis") %} spotify:playlist:37i9dQZF1DWYPwGkJoztcR
{% endif %}
random_song: 'true'
shuffle: 'true'
Just replace the names accordingly (also in the other places) to match everything and then create an entities card with Lovelace. I don’t use the script as an entity, but have created a button with button-card and linked that to the script. i didn’t like the script button (too small and on the side).