Here is how it works for me:
1) Use a TDF release binary, unless you're sure the the Ubuntu-shipped binaries enable the Google Drive feature as well. (--with-gdrive-client-id and --with-gdrive-client-secret configure switches.)
2) Make sure you use the internal file picker: Tools -> Options -> LibreOffice -> General -> check "Use LibreOffice dialogs".
3) File -> Open, then define your google drive: click the "servers..." button, then set type to CMIS, name can be e.g. gdrive, set Server Type to Google Drive, set your username, password, and that's it.
Two notes:
1) If you want to configure the same google drive account on multiple machines, then clicking through these steps is boring. You can edit registrymodifications.xcu in your profile -- all you need is to extend FilePickerPlacesUrls and FilePickerPlacesNames. The URL for gdrive is "vnd.libreoffice.cmis://$NICK%40gmail.com@https:%2F%2Fwww.googleapis.com%2Fdrive%2Fv2%23GoogleDrive/", (replace $NICK with your gmail login) the name is what you want, e.g. "gdrive".
2) gdrive integration works fine for me on master, however I get "general I/O error" when I use the TDF binaries, which is odd -- if gdrive support is disabled, then you should not be able to choose gdrive as a CMIS server type at all.
As for the second note, a bugreport (and CC'ing Cédric) would be welcome. :-)
