ETP's tracking resource blocking can lead to a lot of website breakage (see many examples in Bug 1101005). Tracking resource blocking is currently enabled in ETP Strict mode and Private Browsing mode.
A decent amount of site breakage caused by blocking resources can be fixed by replacing scripts that would have been blocked with our own custom versions of the script that are effectively no-ops. This approach has long been used by a bunch of ad blockers, and is much preferred to allowlisting the resource. As an example of the scripts uBlock Origin uses for script shimming, see: https://github.com/uBlockOrigin/uAssets/blob/master/filters/resources.txt.
This bug tracks all shim script related work.