Karma cannot find Firefox profile [Ubuntu]

### Expected behaviour

ng test should start Karma server and launch firefox browser

### Actual behaviour

ng test does start Karma server, but when launching firefox a popup shows up saying that the firefox profile cannot be found. I can click the localhost link to run the tests, but it will disconnect after a minute or so.

### Environment Details

- Karma version (output of `karma --version`): 2.0.0

### Steps to reproduce the behaviour

I believe it may be because I have the snap version of Firefox, so my profile is saved in /snap/firefox/common/.mozilla/

How do I get Karma to recognize that the profile is there?

Start by reproducing the issue with `ng test` on Ubuntu using the snap version of Firefox, then investigate how Karma 2.0.0 launches Firefox and locates its profile. Done means the Firefox profile popup no longer appears and the test connection remains active without requiring the localhost link.

Written by the indexing model from the issue text.