I'm really bummed out about this. Pissed actually. How is fb able to deanonymize me when...

1. I created an account on it with a pseudonym on a public computer with the sole purpose of browsing the marketplace. So no friends and completely blank profile.
2. I did absolutely nothing on it except search for an item to see how much it's going for...didn't add anyone, look up anyone, join anything, like anything, comment, message...nothing.
3. I used a burner specifically for this account.
4. Didn't install the app on my phone but rather the pwa.
5. I have no non-foss apps on my phone.
6. I use only mobile data with wifi toggled off.
7. I use a famous foss ip changer with a kill switch to not work when not connected to it.
8. I'm using a known OS in this community which works only on Pixels.
9. I'm using this OS's browser.
10. I've added or connected with 0 people on the phone. So no one is on it.

YET....

I see content being recommended to me that I know for sure is related to what someone in my proximity browses. It's very particular. And not only that, but it suggested something to me earlier with a title about a very particular subject that was being discussed by this person and someone else just the other day. I did take a video with my phone which might have captured some of the conversation which contains this topic. But even then, I don't see how fb would get it...considering, well, I'm using this particular privacy oriented OS.

Frustration wouldn't even begin to describe how I'm feeling right now. Could someone please share some knowledge as to how they are doing it? I'd be forever grateful.