> An engineer would find the precise measure to implement - break the UA string sniffing targeting a specific browser.
You got the strategy right but the implementation is laughable, sorry :-)))
The implementation is: "We have a budget of N story points this sprint to resolve bugs, let's prioritize them. Let's prioritize by impacted audience size."
The audience size will make 99% of Firefox specific bugs be deprioritized out of the current sprint. And the next one. And the one after that.
And unless a senior engineer stands up to update the prioritization criteria, plausible deniability forever.