I have been on Firefox for some years now on Mac, Linux, Windows, and Android. Last year the IRS website had some issues, but that seems to be resolved. Otherwise, I've had zero breakages that cone to mind. I use ublock origin, and pivacy badger, and a few other extensions. I wonder if sometimes the issues people experience with firefox are actually caused from their extensions???

If you haven't used Firefox in a minute, I recommend trying it oht again.