I find GitHub "Projects" (https://help.github.com/en/github/managing-your-work-on-github/about-project-boards https://help.github.com/en/github/managing-your-wo

I find GitHub "Projects" (https://help.github.com/en/github/managing-your-work-on-github/about-project-boards https://help.github.com/en/github/managing-your-work-on-gith...) is the most flexible. It is basically boards of columns. Each card can be an issue, or a piece of markdown text. You can use the markdown as a note or as a list of tasks and subtasks. I find GitHub project boards more fun to use than Trello boards, because you can just type and let your ideas flow. Within GitHub project boards, you can also add cards from issues, or you can convert your markdown text cards to issues.