I found this recently: https://americanindian.si.edu/static/education/codetalkers/html/chapter4.html. It’s about First Nationers/Native Americans who were Code Talkers in World War II:
Many American Indian Code Talkers in World War II used their everyday tribal languages to convey messages. A message such as, “Send more ammunition to the front,” would just be translated into the Native language and sent over the radio. These became known as Type Two Codes.
However, the Navajos, Comanches, Hopis, and Meskwakis developed and used special codes based on their languages. These became known as Type One Codes.
To develop their Type One Code, the original 29 Navajo Code Talkers first came up with a Navajo word for each letter of the English alphabet. Since they had to memorize all the words, they used things that were familiar to them, such as kinds of animals.
There were also Code Talkers in World War I: https://www.bbc.com/news/magazine-26963624.
The solution was stumbled upon by chance, an overheard conversation between two Choctaw soldiers in the 142nd Infantry Regiment. The pair were chatting in camp when a captain walked by and asked what language they were speaking. Realising the potential for communication, he then asked if there were other speakers among the troops. The men knew of Choctaw soldiers at company headquarters. Using a field telephone the captain got the men to deliver a message in their native tongue which their colleagues quickly translated back into English. The Choctaw Telephone Squad was born and so was code talking.
I posted about two Code Talkers Roy Hawthorne, Sr. – Navajo Code Talker Dies and RIP Navajo Code Talker Arthur Jose Hubbard Sr (1912 – 2014).
Wikipedia has a more detailed list of other groups of Code Talkers: https://en.wikipedia.org/wiki/Code_talker.
There was even a G. I. Joe Code Talker action figure: https://www.amazon.com/Joe-Navajo-Indian-Navaho-Talker/dp/B00001Z3HW (not an affiliate link).