Any of the respected manufacturers out there, watch for them, check pawn shops and craigslist. I wouldn’t shy away from any Kona/Trek/Giant/Specialized/Norco/Felt/Scott/Cannondale/Novara etc.
A buddy of mine just picked up a brand new Jamis at the bike shop that was two years old for $600. Full suspension and not a bad bike at all. Go see what the shops have in the way back!