> You can spend quite some time configuring firefox not to check for update

Yeah I tried doing this once. I searched about:config for any mention of `mozilla.org` and deleted it. It still pinged Mozilla looking for an update.

You're probably wondering why I wanted to disable updates, well I have a few toy browsers I don't want updated because I like the specific version and some addons I have are not compatible with newer Firefox (due to the webextensions overhaul).

My solution was to use an older version of Waterfox (Waterfox Classic) which still supports older addons. I also use Palemoon for oldskool extension support, but don't use it as my main browser for obvious reasons.