Well, to be complete, DDG also advertises on radio, on streaming, on billboards, and in newspapers. I think TV is the only place I haven't seen a DDG ad.
No, but when they first launched they needed 5,000 users to grow 10%, now they need 5M(?) to grow the same? So investing in other means is probably necessary.
Actually I saw a ddg ad on TV. I started rolling my eyes thinking it was a Google ad lying about privacy but was pleasantly surprised by the duck logo.