Version 5.5.2 of Default Folder X is available. It works on Apple’s recent macOS 11.1 Big Sur beta release.
Amusingly, the biggest problem on macOS 11.1 was the new version numbering scheme that Apple is using for Big Sur. Default Folder X checks the OS version and had always assumed that if the minor revision number (the ’15’ in 10.15.7, for example) changed, it was a major new OS release, because that’s the way it’s always been in the past. Big releases like going from Mojave (10.14) to Catalina (10.15) generally require significant testing and development to ensure compatibility, so it just disables itself and waits for me to finish a compatibility update.
So when Apple went from Big Sur 11.0.1 to Big Sur 11.1 beta (with a version number change that surprised a lot of us developers), Default Folder X said “Oh no, it’s a major OS release! I don’t know what to do, so I’ll just be safe and do nothing” and refused to even look at the Open and Save dialogs. So yeah, redoing the OS-version-checking logic and making a minor functional tweak was all that was actually necessary to get things working on 11.1.
In the process of testing Default Folder X on the Big Sur 11.1 beta, I did find a bug that could potentially cause file dialogs to lock up for what seems like an eternity (potentially as much as 2 minutes), so that’s also fixed in 5.5.2. Because of that, you should update if you’re running Big Sur, even if you’re not using 11.1.
Release notes and download links are on the Default Folder X release page.