Hi @rajtend ,
Thank you so much for your interest in our products and for using our community.
Please let me know if your project with FreeRTOS.
I use MCUXPresso IDE, the version is same as you.
I import a SDK demo "evkbimxrt1050_freertos_hello", add LPUART3 driver, There are no problem and warning.

Please use a project with FREERTOS ,then add LPUART3.
Wish it helps you.
If you still have question about it, please kindly let me know.
Best Regards
mayliu