Bit complaining and background
Since purchasing Homey, I have been somewhat disappointed with the cooperation between Google and Homey. I thought I would be able to make better use of the Google Nest Minis and Audio speakers in my house with Homey. Unfortunately, it feels like playing with Lego and Duplo together; it’s possible, but whether the result is ‘beautiful’ is debatable.
The frustration started with the lack of clarity about which Homey app to use for my collection of Google products. After some searching and reading, it turns out that the Nest Minis and the Nest Audio devices require the Google Chromecast app (@Homey; perhaps include these devices in the description of the app). After installing the app and adding the devices in Homey, it appears that you can do a bit more, but controlling music (via Spotify) still doesn’t work well (action cards not doing what they should, devices not being reachable from Homey, and the points I’m now forgetting to mention).
But wait; there’s also a Spotify app. It states that it doesn’t work with Chromecast. After some time, it turns out you can link a Nest speaker (and also the Hub) to the Spotify app. So, where Homey categorizes the Nest speakers under Chromecast, they do not in the Spotify app description. There is an important requirement for adding a device under Spotify; Spotify must be active on the speaker. Otherwise, the app doesn’t recognize any devices to add.
Unfortunately, even after using the Spotify app, you cannot start music via Homey. This is despite both the Google Chromecast app and Spotify offering action cards for starting music. The other ‘Spotify’ actions can only be used if Spotify is already playing.
I have already spent quite a bit of time looking for an alternative (two Googles talking to each other was really a too strange solution for me) and have finally found a very workable alternative with Google’s routines.
Where I previously used voice commands to have my Google Hub start Spotify and Homey directly play the right playlist, I now have a workable solution for starting Spotify via my dashboard (SmartDash).
Solution
In hindsight, it’s quite simple. Via Homey, I set the volume to 3% on the relevant speaker. A Google routine then ensures that Spotify starts playing. Subsequently, Homey can get back to work (sometimes with a mix of actions from the Homey apps for Google Chromecast and Spotify).
I hope someone can benefit from these insights or help me gain more insights. 
