DefaultApps

Settings ->Apps -> Default Apps Button

I see no way from default apps to add an arbitrary file type or extension default.

Now I think we are supposed to click Opening Links

Then we see a list of Installed App under

Apps that can open links.

Why isn't my app here?

https://support.google.com/android/thread/43145256/how-can-i-open-a-file-in-a-specific-app?hl=en

Android SUCKS

Solid Explorer does not work.

Nothing works.

Nothing shows Dolphin ever.

Nothing knows Dolphin even exists,

https://support.google.com/android/thread/183335643?hl=en