Ozark Trail 29" FS.3 Fastflow Full Suspension Mountain Bike, 29" Wheels, Medium Frame, Fits Rider 5'7' - 5'11", Black, Adult, Online Only

Every youtubers favorite cheap bike https://www.walmart.com/ip/29-FS-3-Fastflow-MTB-MEDIUM/15169117139 (I would personally get a hardtail, because I enjoy riding them)

You'll get much better components on a hardtail in that price range, something like this. You can always go with one of the Ozark Trail bikes too and just upgrade parts as they break or wear out.

This is the most budget friendly bike I would trust on a trail. Ozark Trail Full Suspension