Ask HN: Solo devs, how do you plan your development?

I'm wondering what framework do you use to plan your product development.

Right now I'm using just Trello with a 4 lists, Planned, In-progress, Staging and Production. Works ok but I feel I can do better, like adding a progress % or something to get a better overview of my tasks.

Are you using any agile framework that's simple and good enough for a solo dev (and maybe to support a team of max 3 more devs in the near future)?