Google's Phone app that comes pre-installed on Google's Pixel series of smartphones and Android One devices is a highly sought phone app. There are multiple users who wish to sideload Google's apps but haven't been able to do it. For a non-Google smartphone, the Phone app wouldn't show up in the search results on the Google Play Store whereas sideloading the app would cause the app to crash, and multiple workarounds and modded versions have been circulating to help. But it looks like the Google Phone public beta app is currently showing up for download on a non-Pixel device.
While the Google Phone app is available for download on the Play Store, all devices are not able to find it on the Play Store. XDA Developers has reported that Samsung and OnePlus devices, in particular, are not able to search for the Google Phone app on the Play Store. However, Asus ZenFone 6 users running the latest ZenUI updates have confirmed that they can use the Google Phone app on their smartphones, albeit, a beta version.
The Google Phone app is also reported to work on the Oppo Find X2 Pro and the LG V60 devices. XDA Developers checked the code for the Google Phone app and found that the new app requires the dialler's shared library to be present on the phone. This is not present on Samsung and OnePlus devices which could be the reason that the Google Phone App does not show up in the Google Play store.
If you wish to use the Google Phone app and want to see if your phone is compatible, you can search for the app on the Play Store. You can also choose to sideload the beta app via APK Mirror, to try your luck. At this point, we are not sure if Google has released the Phone app on the Play Store or it has popped up accidentally.