RV64 does not ship with the ability to play ProRes encoded files.
Recompiling requires the following:
macOS 10.12 Sierra or earlier w/ Xcode
Xcode Command Line Tools
Recompile RV64
Edit RV64.app/Contents/src/mio_ffmpeg/init.cpp to comment out the items in the disallowed codecs array.
Then use make to update the file RV64.app/Contents/PlugIns/MovieFormats/mio_ffmpeg.dylib
make
make install
Once installed, double-check RV64 preferences to allow Shotgun integration.
Manage rvpkgs
RV64 rvpkgs can be turned on through the command line.
Packages are located at RV64.app/Contents/PlugIns/Packages. Add these to the optional packages array at the com.tweaksoftware.RV user preference.
/usr/bin/defaults write ~/Library/Preferences/com.tweaksoftware.RV.plist ModeManager.optionalPackages -array-add "\$APPLICATION_DIR/Contents/PlugIns/Packages/$shotgun_pkg"