So this is not a question about how to do this. I know how to do this. I also know that (at least under GNOME) it is neither easy nor intuitive. It involves manually editing several different text files to define MIME types and associating an application with that MIME type. My question is: is there an easy to use GUI tool to do this. I don’t think there is. Associating a file type to open with a specific app is easy, trivial even, to do on MacOS or Windows. Why is this seemingly simple task so hard to do in GNOME?
See comment above from me. This doesn’t work unless you already have .desktop files and MIME types already configured for your app.