A good cheap hardtail to upgrade

I own a 2019 orbea occam am h10 and a trek fuel ex5 and a DMR dirt jumper (older bike with 24”)

Due to having spent all my money of my full sus bikes I’d like to get a cheaper hardtail that I can do all the work to/and upgrade it

I would essentially be replacing most of the parts over the next few years and just want something to ride round the city since I live in a very hilly place and the dirt jumper which I thought would be my solution is going to give me a heart attack trying to ride uphill the bikes I put in the post were the ones I was looking at