This is a frame to hold the OnePlus 8T.
You can print and glue a support/mount that suits your needs and glue it on the back of it like this one https://www.thingiverse.com/thing:631734/files for swivel mounts.
Or this one for generic chinese bike/car holders https://www.thingiverse.com/thing:30104
This v1 is for the bare phone without cover, compact and minimal added size, still, my wife is complaining of the hassle to remove the cover. I might make a version that works with the cover that's included with the phone.
There is no need to use supports
I suggest you to print it in PETG as its flexibility is perfect for this object.
Use a brim (or brim ears) if you're prone to have PETG lifting up!
The author hasn't provided the model origin yet.