If you have Sync 3.2+ you can install the Cyanlabs update file to 20021, but that will not have the necessary Voice Command file 5U5T-14G391-CL.
You could either install the 3.4.xxx to 20021 file and then create a single file installer USB to install 5U5T-14G391-CL or you could merge the...
This is the supposed Sync 3.4.20021 / NA 19 Q1 file list. It was compiled by a user on another site.
APPS = 5U5T-14G381-EB.TAR.GZ <---- Sync 3.4.20021
VOICE = 5U5T-14G391-CL.TAR.GZ <---- Voice Command File for Sync 3.4.20021
VOICE_NAV =...