(Mac) Photoshop CC 2020 now defaults to JPF instead of PSD

Somehow, for some reason, Photoshop started defaulting to JPEG2000 format when I save the file. I have no idea what JPEG2000 is and have never used it. 

1. What changed, and why?

2. How do I change it back?

Been online chat with Adobe for over 30 minutes now. Apparently they don't know either. First, they said to uninstall then reinstall. That didn't solve the issue. 

Anyone else have this issue, and how did you solve it?

MacOS 10.15.5

Photoshop CC 21.2.0