Comment by jhbadger
One of the growing trends these days is solitaire RPGs -- where people play alone as both player and Game/Dungeon Master. Typically this isn't done by AI but by rolling on various tables (sometimes called "GM Emulators"). Not everbody has the time or even enjoys the extrovert pressure of a traditional social RPG. A related concept is the "cooperative RPG" which does have multiple players but no DM so everyone can play.
Here's a list of some of the ones available (about 10 years old but it gives you the idea)
https://rpggeek.com/geeklist/181957/list-of-solitaire-soloab...
This is interesting.
I grew up with “choose your own adventure” books which were like a solo adventure: (If you go on the north road turn to page 34 if you follow the river page 57)
Many board games now have a solo mode with an automated player with tables and dice to help randomness.
https://boardgamegeek.com/thread/3238902/what-is-the-best-so...
Obviously there are adventure video games. Some of the new ones often have interesting back stories, really amazing world building and dnd like adventures. Horizon zero dawn, the Witcher, Star Wars outlaws among many others. “baldurs gate” really gave me dnd vibes (I played through that one multiplayer).