I have to say that I like RT1010 MCUs but documentation is one of the worst I ever dealt with.
In Processor Reference Manual on page 1647 in Table 43-2. there is written that GPT2_CLK is on GPIO_AD_05 which is incorrect. Sadly when I was designing my board I was looking at this table.
Wasnt it yet reported? the last revision of that document is a year old.
There are sometimes discrepancies in the documentation and corrections tend to be made at a very slow pace, so it is always advisable to double check details between multiple sections of documentation and potentially between user's manual and data sheet (plus with firmware headers that often are more accurate).
The uTasker project maintains spread sheets of the i.MX RT 10xx ports/peripherals in a more readable form (also suitable as template for product design) at https://www.utasker.com/iMX/developers.html#pin_mux
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For professionals searching for faster, problem-free Kinetis and i.MX RT 10xx developments the uTasker project holds the key: https://www.utasker.com/iMX/RT1010.html
You are right on this. The GPT2_CLK is available through the GPIO_AD_03 path, not the GPIO_AD_05. I apologize for the inconvenience that this has caused you. I already reported this to the documentation team so they can fix it in the next revision of the reference manual.