I didn't realize that Model apps exclusively use Dataverse. Or is that the intent of the statement. "And [model apps] use Dataverse."? Isn't it possible to create one from SharePoint lists, or even SQL Server? That's an area I know only a little about, though.
BTW, I finally did figure out the mystery of the dataverse connector in my Access 2019 Pro. It turns out that I also have an MS 365 account, through which MS Access is available. However, I had to reinstall Access and specify that MS 365 version to be used. Then I could sign in with that 365 Account and get the full Dataverse experience working as it should.
Not yet impressed by Dataverse, though.
With regard to Pat's question about costs, this LinkedIn discussion sort of sheds some light on that. The gist of it is that licensing is not transparent.