However, there is a way how you can change default app for all files with no file extension found on your Mac.

If you want to change default application with Finder → Get Info option, you will only change the app for the current file. Mac OS X tries to open files without extension with the Terminal app, which often causes an error message that the file doesn't contain any executable data. Change Default App For Specific File Extensions Mac Os.and called like README, READ-ME, INFO, SETTINGS, OPTIONS etc. But often these can also be found as simple text files with instructions, version history, frequently asked questions, settings etc. By default, the Mac OS X identifies files without file extension as Unix Executable File.