I’d echo the suggestion to look at older 26er MTBs. I’ve had a HardRock with a 17” frame for about four years, and that one has now been handed down to our youngest who is 12.
Meanwhile, one of my two bikes is a 22” frame RockHopper from 1988. It rolls great with smooth, fast rolling tires and I use drop bars on it. It really spoils me on our crushed stone trails... I can ride at around 20 mph (in less traveled areas) and barely notice I’m on a rock trail surface.
Otto