Some people like Google Camera. Some people don't. Some people swear by Google camera, some people can live without it.
Over somewhere, there were people that kept asking "how do I have Google Camera on my Xiaomi 13T / Xiaomi 13T Pro", so I guess here's what it is. Basically I'm writing in a more roundabout way, so that you understand the concept rather than giving you straight to the answer (if you want that, just look for the BigKaka link below, its fine).
For the phone, or any other phone, to understand what Google Camera functions that is supported, one needs to install "Camera2Probe" which you can get from your favourite APK store (Google Playstore, etc etc)
After that, just install, run it, and what you really want to hope for is to look for "hardware support level" and pray it is at least "level 3". If I'm not mistaken "Full" would be better.
Now knowing that, now you'll need to go to the google camera repository at https://www.celsoazevedo.com/files/android/google-camera/
and then navigate to:
https://www.celsoazevedo.com/files/android/google-camera/f/configs-bigkaka-07/ Browse to the 13T or the 13T Pro, download both the apk and the config (apply them) and you will have at least, in theory, the best gcam setup for your Xiaomi 13T/13T Pro.
As for why all the trouble? That is because the GCams listed here are just ports. Why are they ports? Here: https://www.celsoazevedo.com/files/android/google-camera/versions/
Do you have a need for using GCam? I don't know. I like it, but I find myself just whipping out the phone, use the built in camera module and then snap away. But it doesn't mean you won't use it, and I'm sure there are many people who like the phone (because the cameras are good) and want to use GCam along with it.
Have fun!