I know it's been said but the bike you need is a rigid 90s mtb from the mid range or above, it really is all the bike you'll ever need, extremely versatile it can be proper hard core trail bike one minute and, with a few minor component changes like tyres and bars, a comfortable commuter the next, some can even be easily converted into bikepacking rigs.
The fact is that if you get the right 90s mtb you will never need another bike, look out for Tange, Ritchey Logic, Columbus or Reynolds 501/531 tubing and any Shimano groupset from DX and above with low mileage, if you want it to commute of haul cargo get one with eyelets front and rear.
Picrel is as comfortable flying down mountains as it is bombing to work, cost me £130 and is just about the best bike I've ever owned, lgihtweight (for a steel frame, 11.4 KG without fenders and rack) and as solid and reliable as anything out there, all I need to do is lose the fenders, rack and slicks and it's ready to be throw down suicide tier rock strewn downhill nightmare trails.
