We have 3 of the older Google Nest Hello Doorbells working in the Google Nest app. You should be able to have 2 of the newer 2nd Gen Google Nest Doorbells in the Google Home app, provided they are wired correctly, or the Google Nest Battery Doorbells.
I have One old doorbell camera and one newer one. The newer one never ran on the old Nest App.
I have one of the older Nest doorbell cameras visable in the nest App, and then I had to create a google home, for the newer Doorbell camera, and then I (think that I ) migrated the Nest app to the Google Home.
I am still having a problem with both the old doorbell and the newer one showing up on the same google home.
If you migrated from a Nest Account to a Google Account, then you are logging onto the Google Nest app using the "Sign on with Google" option using your Google Account. If you are logging onto the Google Nest app and the Google Home app with the same Google Account and the two doorbells are assigned to the same Google Nest "home/structure", then you should see both doorbells in the Google Home app.
This link has some info on migration: