The link in the UI doesn't mention sponsorships anywhere. But this page does:
Who are Mozilla’s partners for sponsored suggestions?
We partner with organizations to serve up some of these suggestion types... For sponsored results, we primarily work with adMarketplace, while also providing non-sponsored results from Wikipedia.
This page links to the adMarketplace Privacy Policy which makes it pretty clear this company is okay with collecting your IP address and passing it to further unnamed entities.
Elsewhere, they say Firefox sends them "the number of times Firefox suggests or displays specific content and your clicks on that content, as well as basic data about your interactions with Firefox Suggest", and then will share interaction information "in an aggregate manner with our partners".
Update: Switched the link from the Desktop to the Mobile version. Added more quotes from FF, and bolded info about their one named AdTech partner.
I'd love to be able to donate to the browser development so they didn't have to do this type of enshittification, but as far as I'm aware its impossible to support the browser itself.
Firefox is foundational to my supply chain for Mull, Mullvad Browser, Tor Browser which i use daily, and I'd be happy to donate for browser development.