Before you buy…TEST RIDE like crazy. You can do all the homework on every little itty bitty detail that you want, and know the performance difference of ceramic versus steel ball bearings, but it won’t mean squat until you go and ride it. I’d also recommend NOT spending near your budget for a bike, especially for your first one after a long hiatus. Especially if you’re not quite sure if you’re going to stick with it. Plus, there’s always something that comes up i.e. you don’t like how the tires grip, seat not the right size, or you want wider bars, or a dropper post, clips and shoes, more well ventilated helmet, etc…these items WILL come up later.
Ask shops if they allow you to put money spent on rentals towards the purchase of a bike, I know that quite a few do, and they sometimes sell their demos at a discount!
I’d recommend a plus bike (larger tire) and a hardtail (front suspension only) as your first bike. IMHO, hardtails are much better in helping (re)teach you how to read and ride the trails, and the larger tire gives you a little extra cushion. The gearing out of the gate won’t matter as much, as you’ll be just getting into it and not sure how much or what the trails are riding. Personally, I ride a 1×11, with a 34 front chainring and a 11-46 in the back. I rarely use the big ring in the back except for when I go west a bit to the mountains. Ride whatever’s on the rental when you get to RI, and find out what you like and what you don’t.
For specific brand/model recommendations, I’ve had great luck with Salsa, the Timberjack in particular is a VERY flexible ride (you can customize and tweak like crazy, and you can run several different wheel sizes if you want), and comes in less than $2k, which gives you plenty of budget left for upgrades! Specialized Fuse or Trek Stache would be great options as well, I’ve either owned or have friends who own.