If you are concerned about using unfamiliar and complex cloud software: A very reasonable option is ccrypt, which gives you dirt-simple command-line password-b

If you are concerned about using unfamiliar and complex cloud software: A very reasonable option is ccrypt, which gives you dirt-simple command-line password-based encryption for text files (or any other files). It's available for most linux distros, cygwin, homebrew, etc. Personally I use my own homemade text editor with built-in AES-256 password-based encryption. It's about as trustworthy as I am, and a tad more friendly than ccrypt. In either case cloud storage is easy; for example a github repo is nice (preferably a private one) because you have backups automatically in case you mess up, which I have done. I don't use my phone for critical work in the first place (can't trust 'em) so I'm not worried about integrating that.