I click allow in the security section (System Software from developer 'Google, Inc.' has been updated) and trigger a restart. To finish the update, you must approve it in the Security & Privacy System preferences A program has updated extension(s) signed by 'Google, Inc.'.
The app loads but then shows two pop ups I tried installing the software and followed all their steps (Reduced Security, Allowing user management of kernel extensions and then restarting after it theoretically updated to allow extensions and changes) but have had zero luck.
Yesterday Google updated their Google Drive for Desktop Release Notes with instructions on how to install a beta version ( 46.0.3.0).