This just caught my attention — P.A.R.T.S.
(Play Alone, Role Together System)

A system-agnostic framework for collaborating a shared campaign for multiple solo gamers. Collaborate on world building, take turns playing solo RPG sessions and contribute to a shared canon.

emelon.itch.io/parts

#ttrpg
#solorpg

P.A.R.T.s. - Play Alone, Role Together system by Emelon

A Pamphlet for Solo Player Who want to Share Their Worlds

^itch.io