I hope one day I can run linux on my phone so that I can use these tools everywhere.

If you're on Android, you can do this today with Termux. I believe you can also set up shortcuts (so you could have a home screen widget to open your TXT file).

That would hand over full control to the author of Termux. According to the play store it is a guy called Fredrik Fornwall. I never heard of him. So I would not trust him with my digital life.