after multiple days of testing node-firefox I came to a conclusion that providing a custom profile from the container filesystem using /usr/bin/firefox -profile argument

- works when the profile is using  cert8.db/key3.db storage

- does *not* work when the profile is using cert9.db/key4.db storage

I created a bug for geckodriver: https://github.com/mozilla/geckodriver/issues/1145

If someone could confirm this, or point me to where the issue is, I would appreciate it.

Martynas