Why do you think google buys the rights to firefox's search bar (as a default setting)?
"The service is free. Am I the product?"
That is a valid thing to ask. Even with FOSS sometimes.
Some FOSS projects are backed by companies, then yes, plausible to ask.
Otherwise, I would answer with a clear no.
(Projects can still collect telemetry and other data and sell that, though the sell part should be very rare, imo...)
Edit: Was that a bad faith argument or a honest question?
Sometimes I can't tell, maybe because of old or ESL...
i would default to this being the truth, until demonstrated otherwise. Call it cynical, but it's the cynical that survive.
To give you an example. Try to use Google Search without sending your data to Google. You cannot use the product without it, you cannot opt out. Firefox, you can use just fine with Google not being your search engine.
It's not a binary toggle - firefox is selling you as a source of revenue for themselves. They're just not making it as extreme as it is possible to be - in the hopes that you don't switch away.
You can compare same situation with safari in iOS. Except google pays a lot more, since you cannot switch away in iOS as easily, and culturally there's more reluctance compared to firefox users. This makes google pay more for iOS traffic, as those users are worth more.
Google is paying Mozilla to be the default search engine. Google is only paying Mozilla because Firefox has users, regardless if they use the default search engine or not. So, indirectly everyone is the 'product'.
I'm sure if 95% of people did swap to ddg, then google may change their mind.
Also I believe there is the possibility Google also pays Mozilla to offer competition so Chrome isn't considered a monopoly (but maybe Edge has changed that to some extent?)
well, a benefit is a benefit. It doesn't really matter how it manifests does it? It's not a donation, as it is not altruistic.