I just use "GM" without translation, since most people understand it. Sometimes I use "Facilitadore", since also the term GM is pretty horrible, even in English to me, lol.
Yeah, I also dislike GM. Usually I prefer Narrator or I simply say "who directs". But the last one is clunky and narrator is also gendered in spanish.
I guess I'll use the "e" as neutral and anger some rancid people haha.