with a typical iPhone + macOS combo, you can enable SMS via Messages app by enabling a setting in the System Preferences. I use this and frequently receive all SMS messages via this route.
Just so I'm clear, this isn't just using iMessage, but it will actually bill my provider when messaging in the mac app?
yes indeed, not just iMessage. It works even for when I message for example, my father, who only has a basic SMS plan with an Android phone
Thanks for the info. Does the phone need to be plugged in? Turned on? Or enabling the setting is sufficient?
The phone does not have to be plugged into the computer if that's what you mean. I haven't tried it with the phone turned off, but I would suspect it could be handing it off to the phone somehow, that might be what is happening. But once I enabled the setting it worked as described.