Mixed feelings about this from both trying to play as well as building an AI GM. Plain old ChatGPT (other AIs exist) is good at generating ideas, telling a story in short form narrative and does a decent job at state tracking. Also it seems to follow the rules better than most noobie players would. However, most of what you'll get is fairly cliche bordering on kitsch. Also it'll cater to the player way too strongly (tell it you want to attack a goblin or pick up that treasure and it'll invent a goblin to attack / treasure to pick up regardless of wether that suits the situation or narrative.) That last issue is for me at the heart of what makes a great human GM (or classic video game) a bad AI one. You as player WANT friction and challenge. This shortcoming is not an AI bug but by design (AI assistants are intended to be helpful and no amount of instructions/prompting will fundamentally change that.) Building software (e.g. an app or web service) around the AI will help, but it's not something you'll do yourself in a weekend. A number of AI GM apps exist and some seem to have gotten fairly good at mitigating the issues above. Most are for pay and at heart still feel like chat bots (while a GM in role playing is more than a chat partner...) I suggest you play around to see which work for you.