TL;DR: it no longer works, but in theory, it is doable. Read on!
Even though there’s limited availability for the Mate 30 and Mate 30 Pro, mostly to China, which doesn’t have Google access anyways, and to international press review units, the community is hard at work. It was initially possible to install Google Play Services and Google Mobile Services on the Mate 30 and Mate 30 Pro, for about a week or so, with the help of LZPlay, but that method is no longer available.
There’s a new method, as the community gets involved. This method implies downloading a file which is no longer available due to copyright issues, but the method, in theory, works. It involves backing up a device which already has GMS installed, and restore those files to a fresh device (or one that has been reset).
You can find out more specific details over at the source link below. The key takeaway here is that this is no longer about the U.S., China, Huawei, or Google. Once the community gets involved, and the great minds at XDA Developers forums, the challenge has to be completed. According to the current status quo, there’s no way of legally installing GMS on a Mate 30 series of smartphones, nor for Huawei to officially endorse such activities. However, what you do with your own device is completely up to you.