Comment 5 for bug 1823917

I will say, though, that there are many examples across various Linucies (that's the plural, right? ☺) suggesting to use the BROWSER variable to change the default browser. Case in point:
https://wiki.archlinux.org/index.php/Environment_Variables#Default_programs

And I might add another point: it's obvious that chromium-browser uses `xdg-settings` but I'm not sure what firefox uses, but the end result is that the `xdg-settings`, `xdg-mime` and `$BROWSER` values are all set appropriately. I will note, too, that `xdg-settings` results in a proportional change to `xdg-mime`.

I do think that setting BROWSER is problematic and it is contributing to the problem, but the fact that chromium-browser seems to be unique among other browsers in terms of lacking robustness to set itself as default regardless of circumstances. Therefore, I think the fault lies with it.