The days of the 0% for X months financing are coming rapidly to an end as inflation and the federal reserve interest rate both go up. But even those loans, while they incentivize the buyer to pay the loan off early, will still apply interesting -- sometimes, if you're not careful, all the deferred interest for the past X months, which is extra shitty -- after the 0% period is complete. I think the only major manufacturer this season that's offering any sort of 0% deal is NIssan, and they're sort of going all in, probably in an attempt to move excess inventory.
It's just not a thing to see a lender not charge interest. It's like, going to Taco Bell and ordering a burrito for $0.
There are, of course, some exceptions. The dealer may be subsidizing the interest payments. The lender/servicer may be pulling some (probably) illegal shit and calling "interest" a "service fee" or are perhaps charging a "payment processing convenience fee" to make their money. The dealer / automaker may be paying the servicer's bills on the backend, but don't think for a moment that cost isn't baked into the sale price of the vehicle. I just can't see a case where a lender would be okay working for free.