If you didn’t liked any suggestion above, remind that you can use it as Stream Deck controller or a similar remote controller like that.
Being said, iPhone 13 is still a very, very decent phone. Consider passing it to family’s elders (there’s an ‘old person’ mode on all iDevices). Also StandBy mode is great.
Won’t you consider board game classics? Catan, Munchkin, Ticket to Ride, Exploding Kittens, Wingspan etc. are pretty good choices, albeit not “solo”, all have free/online versions somewhere.
Also check BoardGameGeek for “solo games”. Their ranking are most often pretty spot on.