Hi,
There are a lot of famous smartphone brands without GMS certificate. Here are some examples: Ulefone, Zopo, Oukitel, Vernee, Doogee, Blackview, Cubot, Leagoo, VKworld, HOMTOM. Some of them are not so advanced but much older brands than UMI.
As a result of the non-certified device, there are problems with accessing the Google Store for downloading and updating the app. On my Umidigi S whom I have about a month now it's a real problem!
Query on Umidigi Maker: Will Certification Be Performed?