I finally found the URL and got it to work with Home Assistant using this script:
play_svt1_on_chromecast:
alias: Play SVT1 on Chromecast
sequence:
- data:
entity_id: media_player.chromecast__kok
media_content_id: https://svt1-b.akamaized.net/se/svt1/master.m3u8
media_content_type: 'audio/mp4'
service: media_player.play_media
play_svt2_on_chromecast:
alias: Play SVT2 on Chromecast
sequence:
- data:
entity_id: media_player.chromecast__kok
media_content_id: https://svt1-b.akamaized.net/se/svt2/master.m3u8
media_content_type: 'audio/mp4'
service: media_player.play_media