Below is only anecdotal evidence that Spotify is linking to your off App/logged in browsing history to your Ads profile.
Just had an egregious (or just impossibly coincidental) privacy issue.
On my separate work machine, I had the Spotify app, logged into a work created profile. That I barely use, and when I do it's quite standard popular English language songs. I've had it set up for a long time, and never really noticed any ads it served me.
Also, all my work is english language, my other apps. Nothing strange installed as it's a work machine to do the basics.
The other day, for a joke to a colleague, I was looking some German translations. Not long after, I get a completely German language advert played to me.
Felt a lot like Facebook serving ads by listening to your mic.
The search was done on DuckDuckGo using Firefox.
On Firefox and Spotify I have all my accounts set to not use personalised ads etc with as much of those settings turned off as allowed. I also have reject/opt out of cookies and all that jazz by default.
Has anyone else experienced this, what level of tinfoil should I eat?