Earlier this week, Firefox 87 arrived with SmartBlock for Private Browsing — a new intelligent tracker blocking mechanism that provides stand-in scripts to decrease the chance of a website breaking on load. The list of other changes includes a new default HTTP Referrer policy, full support for VoiceOver in macOS, and more.
https://www.notebookcheck.net/Firefox-87-now-available-with-SmartBlock-as-well-as-many-minor-fixes-and-tweaks.529277.0.html
I don't use Firefox much since switching to Edge. I did try Firefox 87 on two different PC's the other day and found that some web sites worked great while others seem to load sporadically and at times seemed to pause loading. I assume this may be the result of all the anti tracking and privacy features? SmartBlock seems like a feature added to fix what the strict privacy feature breaks. I sort of gave up on this whole privacy focus and just decided I wanted a browser that just works.
SmartBlock deez NUTS.