When was os 11 release for 5t
Never, the 5-series of Oneplus is EOL (End Of Life) and won't be receiving any further updates.
Please, next time use the search before creating a new thread, there are similar threads already open and answered.
If you want to update to Android 11, you need to install a custom rom.
[Community Workshop] Vol. 1 – Photography with Nabil Rosman
by Nabil Rosman, 2021-05-06