Wondering where Firefox's 'system' add-ons went?

There are several built-in add-ons (aka 'system add-ons') that ship with Firefox which are installed without users' knowledge or consent and they have been used for controversial purposes in the past. On a Linux box, they used to be located in /usr/lib/firefox/browser/features/ where any offending ones could be easily deleted, but as of Firefox version 138, they've been incorporated into the /usr/lib/firefox/browser/omni.js compressed archive which makes them less accessible. Once omni.js is extracted, one can find them in /chrome/browser/builtin-addons/. While those which the user may not want can be deleted from the omni.js archive, they will be reinstalled when Firefox is updated.

Of particular interest is what appears to be a new add-on, 'search-detection'. Not being a JS wiz myself, i've asked a couple tech friends if they'd be willing to have a look at it, but it seems to me that Mozilla is very interested in search URLs and what extension, if any, is providing user searches.

While there is a group policy for handling these built-in add-ons, it didn't seem to work for me in the past and i'm not sure it's applicable to Firefox versions 138+.