No, Gungi Is Not The Only Star Wars Wookiee Jedi, Though They Are Rare
"Star Wars" has one of the biggest and most fleshed-out universes in fiction, one with countless worlds and characters that each come with their own stories that make the universe of the franchise feel lived-in.
A lot of it comes from the movies, sure — particularly the prequels, which changed our understanding of the originals by fleshing out the Jedi order as a corrupt police force and making the Emperor an elected official. But it was in the TV shows, the books, and the games that "Star Wars" became what it is today. The movies implied more than they explained, introducing cool characters that never uttered a word but still looked like they had a story to tell — which writers would then expand later on.
Take Chewbacca, one of the most memorable characters in the franchise, but one we know extremely little about in the original movies (unless you count the "Holiday Special," and why would you?). Of course, that didn't stop writers from trying to explain what made Chewbacca and the Wookiees unique, which led to a bunch of Wookiees wielding lightsabers.
In the current canon, Wookiee Jedi are extremely rare, but they still exist, most famously in Gungi, a young Wookiee Padawan introduced in "The Clone Wars." But in the recently released book "Star Wars: The Secrets of The Wookiees," we got a proper list of Wookiee Jedi across the history of the galaxy. This includes Gungi, but also Arkoff and Burryaga from the High Republic titles. The last one made headlines when he was introduced wielding a huge lightsaber, and in the book, it is revealed that Burryaga is a friend of Chewbacca's family, a fact he is quite proud of.
There is one more, however, which we haven't seen yet. Kelnacca is set to appear in "The Acolyte."
A Wookiee with a lightsaber
Before the current canon, there were a few Wookiee Jedi, like Lowbacca (very original name, I know) until George Lucas himself made it a mandate that there would be no more Wookiee Jedi.
According to Lucasfilm's Pablo Hidalgo, it was after concept artist Derek Thompson suggested a Wookiee Jedi for "Revenge of the Sith" that Lucas decided to roll back on the concept. This likely happened as a way to prevent an explosion of more Wookiee Jedi while Lucas developed the planet of Kashyyyk for the last of the prequel movies. Eventually, he went back on this and decided Wookiee Jedi were rare rather than existing, which is why the droid Huyang comments on how rare Gungi is among the Jedi ranks.
This is far from the first time Lucas has gone back on one of his own mandates or ideas for the sake of a cool moment or character. There's the time he suddenly decided Maul wasn't dead anymore, despite being vehemently opposed to the idea for years before that. Like with Maul's return, "Star Wars" is better off with Gungi in it, because the idea of a Wookiee Jedi — especially that being rare — is just too fascinating to pass up.