Just got the Mate 30. Didn't try to sideload GMS. However, I still need to sync my google email, calendar, contact and hopefully google task. For email and calendar, I install the microsoft outlook apps, and the built in sync function do support google mail and google calendar. For the contact sync with google, I use DAVX5, which can be get for free from F-Droid. DAVX5 using calDAV and cardDAV to sync your huawei calendar and huawei contact with google calendar and google contact. However, I am yet to find way to sync google task.