How to set the default browser in OS X?

Question

macOS

In OS X El Capitan 10.11.6, and it was before, the default browser constantly crashes.
By default, I want to use FireFox, I almost always have it running, for many days in a row. I do not turn off the computer, at night it only “falls asleep”.
It often happens that links, say, from Telegrama, instead of opening in a running FF, suddenly start running Safari or even CyberDuck (FTP client). When I open System Preferences - General, the browser selection menu is empty!

Screenshot of the General panel

A long series of operations helps to fix the bug:

1. close firefox
   
2. launch chrome
   
3. allow Chrome to become the default browser
   
4. close Chrome
   
5. launch firefox
   
6. allow FF to become the default browser
   

After that, usually FF becomes the default browser again, and a list of browsers installed on the system appears in the menu in General. Although this list is not always complete. For example, FireFox Development Edition does not always appear there.
There is not even a guess what could lead to such a failure. I have not found any solutions yet, except for multi-browser dances.
Tell me what causes this cant and how to fix it correctly?

Answer 1

The failure could occur at the time of installing all browsers. When first installed, each browser tries to hang itself as the main one. And he actually asks about it. Perhaps you have mistakenly set several default browsers and due to some system glitch (or the persistence of some browser) it crashes every time you visit.
Try uninstalling everything and reinstalling. When asked again for each, indicate "no no no!" and only "yes" for Firefox.