How do you get "trapped" in it? I've never used it seriously, but my last experiment on Android requires you to create a folder to write Markdown files to. Which seems about as portable as any app can possibly be; it could disappear from your devices tomorrow, and you'd still have all your stuff, right?
FWIW Markor also lets you edit Markdown files locally on Android, and it's probably a far cry from Obsidian but it could easily serve as a drop-in replacement in such a scenario.