I got some XT M785s at a decent price second hand (about deore price) – they can’t have been used for more than a ride round the car park if that.
They were cheap enough that a new caliper or lever could be funded if needed. Plus the internet says they’re more reliable than later versions (not that I necessarily believe the newer ones are that bad, but I know people who’ve had plenty of problems.).
I’ve run basic non-series Shimano brakes too, and they were fine, not as powerful but perhaps that’s the age of the brakes more than the model. And very cheap, if you want warranty backup the only issue with them is they’re so cheap it wouldn’t be worth the hassle.
As a side note I’ve had other brakes second hand very cheap or free from friends that have had hard use and then I’ve not used for long as they’ve needed a bit of sorting out and I just don’t have the time!