Everything I open will open in this cretain of a browser called Epiphany. Discord, Thunderbird, etc.. all Links open a new instance or tab in Epiphany. I do want to open everything only in Firefox. I can't be the only one. How to mitigate this issue?
In some instances, the program you want to define as default does not appear on its category menu drop-down in
System Settings > Applications > Default tab
Another way is to right click on a file with an extension (for a web browser, that would be a
.html file), and set the program to be used in Properties.