macOS Catalina has a number of security features that prevent the running of malicious code. However, it can inadvertently block useful software too. In this case, it’s blocking the FUSE kext that Keybase uses to access the encrypted files stored in the cloud. Normally, you can go into System Preferences / Security and allow usage but in this case, the GUI would not allow access.
The first step is to find the kext bundled with Keybase that is causing the problem. On my system, Keybase is stored in the main Applications folder.
$ find /Applications/Keybase.app/Contents -iname kbfuse\* /Applications/Keybase.app/Contents/Resources/KeybaseInstaller.app/Contents/Resources/kbfuse.bundle /Applications/Keybase.app/Contents/Resources/KeybaseInstaller.app/Contents/Resources/kbfuse.bundle/Contents/Extensions/10.11/kbfuse.kext /Applications/Keybase.app/Contents/Resources/KeybaseInstaller.app/Contents/Resources/kbfuse.bundle/Contents/Extensions/10.11/kbfuse.kext/Contents/MacOS/kbfuse
Then it’s simply a matter of removing the
com.apple.quarantine extended attribute from the kext:
$ xattr -d com.apple.quarantine /Applications/Keybase.app/Contents/Resources/KeybaseInstaller.app/Contents/Resources/kbfuse.bundle/Contents/Extensions/10.11/kbfuse.kext
Next time Keybase starts, the kext will be loaded and the functionality of browsing Keybase files in Finder (and the command line) will work.