I just placed an order for the 9T pro, after loads of research. It pretty much ticks every box of what I was looking for, although I would prefer something closer to aosp (and I'll probably dabble in custom ROMs when it's better supported by something like lineageOS).
The regular 9T is a bit cheaper, and main difference is it has a less high end cpu/gpu, and at least one of the camera sensors is a lower resolution variant, but yeah if you don't need/want the high end 855 then I think the 9T is a solid option.
Nice to get a midrange budget, high spec phone with a 3.5mm port.
I can provide more impressions when it arrives next week, but I have been impressed with xiaomi devices in the past (in upgrading from a Mi A1), and reviews are all very positive.
In the UK at least, I didn't have to pay much more at all for the 9T Pro vs a 9T, but I don't know what prices are like elsewhere, and the 9T is no slouch either.