I've never tried Kiwi Browser but had similarly come across it while searching. The dev themselves refers to them as ads[1] (2022), though prior to being accepted properly into Bing's referral program Kiwi redirected all search queries through their own servers[2][3] (2021) (the original Kiwi repo's issues tab has been deleted since).
Tbf the dev always sounds reasonable in their responses but was a little off-putting initially so I kinda understand the GP's impression.
Then the main dev is just wrong. That issue contains the exact words "Since then, now Kiwi Browser contains ads" as an explicit reason why they can't be in F-Droid.