It's a rooted option and doesn't apply to this thread but to summarize if curious.
Magisk repository install "Google Dialer Framework"
Now you'll be able to install the app and get updates right from Play Store as if you were a Pixel phone.
To get visual voicemail working need two things...
1.) Install Google Phone as system app (once again need root and "app systemizer" Magisk module to do that systemlessly).
2.) Edit the dialer_phenotype_flags.xml file located in data/data/com.google.android.dialer/shared_prefs. Change values to from false to true in areas relating to your carrier and vm (voicemail).