browser - how do I stop firefox from notifying me about updates?

I have Firefox 56, the last good version of the browser, where things I need in terms of performance, and functionality both still work. Im not going to update, EVER. (There are other browsers out there, but firefox worked so well for scripting.)

anyhow, Firefox keeps allerting me about updates. I have turned the updates off, in about:preferences

but firefox keeps bugging me. with notifications like these:

and this:

I dont want to keep getting bothered by the notifications, how do I make them stop?

Answer

From experimenting with Firefox config, just as a possible addition or alternative when solutions that have previously been suggested here are not enough.

After opening the about:config (typing about:config into the address bar and then pressing Enter), apply either or both of the following config items:

• Search for app.update.silent, then set it to true


• Search for app.update.url, then change it to a fake/non-existent URL
  

  
  

  For example, if the original is https://aus5.mozilla.org/update/6/%PRODUCT%/..., I changed it to xxxhttps://xxxaus5.mozilla.org/update/6/%PRODUCT%/...