How to start Firefox in english on a german system without changing the langage settings?

Question

I'd like to start Firefox in english in order to figure out a large amount translations of error messages without doing research. The usual suspects LANGUAGE=en, LANG=C, LC_ALL=C don't work.

I had trouble with this task for other programs, but the solutions don't apply here:

• How to start ubuntu-software in english on a german system without changing the langage settings?: The "solution" if you can call it that was to reconfigure the program with dpkg which doesn't help in this case
• How to invoke a KDE application with another language (equivalent of LANGUAGE=C)?: Firefox is not a KDE application

Afaik it'd be nice if LANGUAGE would work for Firefox since it's a comfortable reliable solution to overwrite the system-wide configuration for a single invokation of the program. I guess opinions on proposing its support as a feature doesn't go beyond the scope of this question.

I'd like to leave both the Ubuntu and Firefox settings untouched.

I'm using Ubuntu 19.04.

Answer 1

The LANGUAGE variable is ignored by Firefox, but setting LANG or LC_MESSAGES should work.

• Press Alt+F2

• Enter the kommand:

  env LC_MESSAGES=en_US.UTF-8 firefox