Solo TTRPG games you can play on your phone for free
Text dump inbound.
The sensible answer would be to play a videogame. On Android, the free options that are D&D-adjacent are usually roguelikes, MUD and one of the hundreds of RPGMaker games. If you're ride or die for D&D, they made a fair share of Dungeon Crawlers for the GBA and older systems you can play pretty comfortably on your phone. At the end of the day though, as Manko said above they're generally pretty different experiences from TTRPG. AIs using GPT-3 try their best, but if they didn't convince you back then they might not really change your mind now.
The other sensible answer would be to just write your own fiction.
In-between these two options however there is a
autism spectrum of increasingly niche hybrids that try to pull off solo RPGs in their own way.
TTRPG Modules
There's nothing really stopping you from finding a D&D module and just playing it by yourself. Hell, D&D has tried to publish (with varying degrees of success) several modules specifically intended for solo play. Almost every RPG system tends to have some modules, and most of them tend to be quite thorough in their options that you can pretty much play them on their own, particularly the older ones. There are also places online that publish their own original modules you can run.
When you need to fill in story gaps that aren't clarified within these modules, the most common tools people use are random tables, the
Mythic system, story dice, Tarot decks etc. There are also entire TTRPG systems, like Ironsworn, that are designed to be played on your own. Almost all of them are based on the same principle of using a premise to give the story structure, using some kind of randomness generator which can give you multiple vague answers and interpreting how this applies to your character in this specific situation, like you're an ancient fortune teller.
You could argue that TTRPGs played this way are pretty much combat systems and skill checks with a freeform Choose Your Own Adventure tacked on, and you'd be right. Speaking of which-
Choose Your Own Adventures
The highest form of literature. There's like dozens of these on Android, dozens more were published in the 80s and pretty much every single Visual Novel counts. Since they're pretty well-known it's probably not exactly what you're looking for, so this is more of a heads-up that a large number of them have been ported directly into a phone format. Since they were big at the same time as D&D was big, I doubt there isn't some official D&D or a thinly veiled clone book lying around.
CYOAs
Confusingly called in the same way as the books despite only sharing the fact that they are both very niche, weird mediums. These are more along the lines of Character Creators and structured story prompts you imagine/write about, and evolved from those "would you rather" and "choose a character to protect you" forum games. An example would be something like this: (
1,
2,
3,
4). Their main draw is that they're literal .JPGs and .PNGs, can be posted on forums for discussion but are "played" on your own, and there are
thousands of them covering a range of genres, quality, length and horniness.
Insanity
If you're really feeling crazy, you can consider posting in online game threads looking for random strangers that share your time zone on places like forums, Discord or Roll20, with all the potential garbage that doing so entails. The bottom line is that TTRPGs like D&D revolve very heavily around socializing, and any system that tries to emulate that with only one person tends to be a very different experience no matter how you cut it. Otherwise you can only wait around for GPT to keep improving.
