Google Messages is one of the prettiest and most useful messaging apps in the Android world, so it's no surprise that some people download the app as a replacement for their pre-installed default messaging app on phones that don't ship with Google apps. It looks like they might soon not be able to use Messages anymore if they don't have a certified device. XDA Developers has uncovered a string that points to a March 31 deadline when the app will stop working on phones without Google services.
The string is as clear as it can get. If Google pulls through with the certification requirement for Messages, users with uncertified phones might soon see the following message in the app: "On March 31, Messages will stop working on uncertified devices, including this one." This should only affect a small fraction of Android phones that don't ship with Google apps, like recent Huawei phones or Android phones with Chinese ROMs.
Google Messages is one of a few Google apps that work on uncertified devices without Play Services, likely because it relies on the SMS and RCS protocols and doesn't require logging in to your Google account. XDA Developers suspects the move comes following the RCS end-to-end encryption rollout since the company can't guarantee that an uncertified device isn't compromised.
If Google pulls through with the change, people with uncertified phones will soon have to look for another solution. Perhaps Signal could be a good choice — it supports sending and receiving SMS in addition to its chat service.
Source: Android Police