@Cy one of the awesome things about cycling is you can change a lot of things on your bike to set it up the way that you want it. In order to best talk about options I need to ask some qualifying questions. Do you already have a particular bike in mind? If so what specific parts do you want to change (ie going to a 1x in the front? or changing the 'level' of the drivetrain) There are a lot of options but with so many different standards there is no simple answer. In helping customers in the past I would always recommend getting the bike that comes the closest to the setup that you want, you will have fewer parts to change and usually comes out as the most economical way to do it.
Ride safe out there!
@REI-GregM I am a beginner and will be a first time to buy a mountain bike. I am 5’6.5” height , want the shimano xt for the drivetrain and brake set. 1x in the front and 12x at the back. 29 wheel size. I would prefer a cannondale brand hard tail mountain bike. The price range is $1500-$2000 .
@Cy I have been looking around to see if anything meets all of the criteria that you are looking for. One of the closest is the new Salsa Timberjack XT 29. The drivetrain is mostly XT and it is 12 speed. The brake are Shimano but not the XT line.
Cannondale has a Trail 2 29er but the only part on it that is XT is the rear derailleur. But that model only has 11 speeds. Both are great bikes. Good luck in your search!
Perhaps someone else will chime in with a bike that more closely matches what you are looking for.