How to start music playback on smart speakers (google home)

I am using Home Assistant for over two years now and included a roborock and smart thermostats but with this topic i am lost like never before:

I am having Harman Kardon Citation ONE Smart speakers and just want to start music playback
on the default configured music service (in my case spotify - free) and it should start a random playlist.
Basically the same as if i would say “play music on device < devicename >”.

The speakers are configured by the google home app but also support chromecast streaming but i would prefer not to use chromecast streaming here.

From what i already read somebody tried starting playback by the google home sdk somehow but this is a action that was blocked. But the statement was from 2018 (is it still up to date)

The other way seems to be to use spotcast together with the spotify-card and the spotify player integration. But from what i read this only works with spotify premium and it can’t do the default playback approach i described above.

On starting the playback by voice the attributes of the media player device look like this:

media_content_id: spotify:track:xxxxxxxxxxxxxxxxx
media_content_type: music
app_id: xxxxxxx
app_name: Spotify
supported_features: 21439

Is there a way to accomplish what i plan to do?

There are some ways to accomplish that goal. However, the most limiting factor will be the Free Version of Spotify. You can give the custom component Spotcast a try. Not sure if this works with free spotify in the meantime. The only other reliable way i know off, is to run a custom GoogleAssistant Webserver (there are some tutorials in this community) that allows you to give commands via http (text) the same way as you would speak them to your speaker. It basically gives you an additional Virtual Google Home Speaker in your Google Home App.