You can probably get away with it on any carrier judging by my experience, either by activating a whitelisted device then SIM-swapping (has so far always worked for me on verizon with unapproved devices), or calling and playing a little hardball with the customer service people like this guy did on AT&T: https://youtu.be/qZqp9EXYNjU?t=801
But yes, t-mobile and their MVNOs should work fine as long as it has the right bands, I've used random devices on tmobile and mint mobile with no hassle
more possible at&t tricks listed on here: https://old.reddit.com/r/Xiaomi/comments/x6g2ve/xiaomi_phones_do_not_work_on_att_in_usa/jye7xrd/