Long story short: That pop-up you get when you open Firefox (or whatever other browser) for the first time asking you if you want to make it your default browser won't work anymore. They're forcing you to go through their convoluted control panel where you have to change it like 20 times for each file extension.
Lol I'll never get over the fact that they were forced to put Netscape navigator in the install media back in the 90s because they simply included IE on the disk.
Simpler times.