In the address bar, type about:crashes<enter>. Note: If any reports do not have BP in front of the numbers/letters, click it to submit them.

The crash report is several pages of data. We need the report numbers to see the whole report.

Using your mouse, mark the most resent 7 - 10 crash reports, and copy them. Now go to the reply box below and paste them in.

That's what appears in about:crashes :

Segnalazioni inviate

Non è stata inviata alcuna segnalazione.

(In English: Submitted Reports. No reports)

Maybe this appears because when Firefox crashes for Hello, it does it suddenly without creating a report (with the appearing of the related dialog box)? Maybe Hello doesn't recognize the camera and mic? I don't know.

Start Firefox in Safe Mode {web Link} by holding down the <Shift>
(Mac=Options) key, and then starting Firefox. A small dialog should appear. Click Start In Safe Mode (not Refresh).

Is the problem still there?

Well, I started the safe mode, now Firefox doesn't crash when I login into Hello, but, as before, Firefox can't make Hello work because it says "No camera or mic available"… it's like if it doesn't recognize them, in Xubuntu the camera and mic work

ETA: They work also in other browsers…

ETA 2: I gave the site "hello.firefox.com" the permission to use camera and mic, too…

I've called the big guys to help you. Good luck. Do not use Hello until they answer.