Ironsworn is probably one of the most popular solo tabletop RPG, and it's free. (It can also be played wth or without a GM). You play heroes going on perilous quests in a harsh low fantasy land. You can customize the setting by answering a set of guided questions with chosen details. The character generation is simple. The way for characters to advance is to swear an Iron Vow and face challenge to progress, which really help directing the gameplay. There are robust tools to help you when you feel stuck.
List of free Ironsworn tools
Ironsworn character generators
Character:
( Alina )
List of free Ironsworn tools
Ironsworn character generators
Character:
( Alina )