Hm, good points. I’d add: If you open a new tab in firefox, there’s google’s search engine pinned, so you can see (and use) that trade-based service easily. Plus they support this function of @google in their tab to make an easy search via google. Because of all these points I’d put them into the category rejected. Promotions (trades) are a slippery slope, because once you do them, you depend on them. And sooner or later google might say to firefox: I give you some more money if you give me some data of your users…

Firefox is also getting paid to decide what default search engine to use. This is a direct trade. They want your attention 100%. It is hard for me to label Firefox as trade-free… https://www.investopedia.com/articles/investing/041315/how-mozilla-firefox-and-google-chrome-make-money.asp

Firefox promotes its trade-based service Pocket https://getpocket.com/premium on all tabs. They also promote their file sharing service that offers premium (paid) options. So be aware of these.

I agree with that, so 4 out of 5 blocks. As a side note you can opt out from that: in the Privacy & Security panel ->

Scroll down to the Firefox Data Collection and Use section and uncheck the boxes where it says “Allow Firefox to send technical and interaction data to Mozilla”

Firefox does collect some data but mostly for technical purposes https://www.mozilla.org/en-US/privacy/faq/ – so you trade some data to them.