As much as I don't like the new Unity policy I think this is actually covered by the "No, in this case the developer is not distributing it so we’re not going to invoice the developer" FAQ answer given in response to a question about what happens if your game is install distributed through a subscription service like Xbox Game Pass. For a developer it might be worth getting that exact question answered in writing though.
FWIW, Privacy One Group Ltd has "invested" in Startpage since January 2019. Privacy One Group Ltd is a separate entity operated by System1, an advertising company. Startpage does still seem to get regular 3rd party audits to keep everything in check though.