It’s still never been proven despite countless very smart people looking for this exact behaviour for well over a decade now. The first person to actually prove this whole mass spying via microphone to sell ads thing is actually happening, would be world-famous overnight.

For instance on an android phone, it’s not really possible for an app to do something that a determined enough security researcher couldn’t ultimately detect if they were looking for it. When you can build your own version of the operating system and decompile the application easily, there’s not really any other places to hide that won’t give something away.

If you feel like your phone is acting off of a conversation you had without interacting with it, it’s nearly always one of these three:

• The vast majority of people are super predictable most of the time.
• You are not accounting for other people in the conversation, who may well have just googled the thing. These companies know who you spend time with, they don’t need a microphone for that.
• Baader meinhof phenomenon

Don’t get me wrong, I’ve thought surely something fishy was going on plenty of times, but the reality is, until someone can actually prove it (which is entirely possible to do if it’s happening), it’s gotta just be the above. We’re being tracked a crazy amount, but it’s not passively by microphones in our pockets

Note: none of this applies if you’re actually being specifically individually targeted (i.e. by a hostile government). All bets are off in that instance