There was a Diablo Immortal update in Google Play in March 29. At least 3 people confirmed their Google Pixel 3a was again seeing the app and their pre-registration showed up.
Most of the people who pre-registered back in November 2018 up to December 2 2020 started to get the error: "Your device is not compatible" or the Diablo Immortal app was no longer visible in their Google Play search after December 3, 2020 -- which introduced an adjusted compatibility list specifically for technical alpha.
In preparation for Diablo Immortal Beta, the March 29 update seems to have lightly increased the compatibility. In theory, devices with Snapdragon 670 up to Snapdragon 710 should now be compatible.
Please, visit Google Play in your Android device. Search for Diablo Immortal.
If your device has Snapdragon 670 up to 710 and you can now see the Diablo Immortal app + pre-registration let me know your Phone name and model (i.e. Samsung Galaxy A70, Snapdragon 685).
If you have a device older than Snapdragon 670 and now it shows Diablo Immortal in Google Play and the device is now compatible let me know.
If your device has 710 or better but it became incompatible in December 3, but now it is back as compatible let me know.