Message a Contact Group

There are some instructions ~ details in each of these pages may help:

• Send a group text message on your iPhone, iPad, or iPod touch - Apple Support

https://support.apple.com/en-us/HT202724

• If you can't send or receive messages on your iPhone, iPad, or iPod touch - Apple Support

https://support.apple.com/en-us/HT204065

• Leave a group text on your iPhone, iPad, or iPod touch - Apple Support

https://support.apple.com/en-us/HT209430

There are articles that say how one can set up and then move your messages

to 'non-Apple SMS' phone ~ that hasn't a native ability to use iMessages.

My experience is limited, regarding your question. Most non-apple cell phone

users I know have access to all features that messages allow; just that they're

unable to enjoy the 'better feature set' & higher security that iMessages afford.

[I've gotten a few mixed recipient Group messages, with at least two, and up

to four non-Apple product users. My preference is to avoid Group messages.]

Not sure how that works, since even an early iPhone SE such as I have, can do

iMessages and takes calls/messages from Android (& etc users) as SMS. With

later iOS 13.4.1 and older Mac OS X El Capitan, I can still use iMessages; and

since the 'hand-off' between these allows me to use Mac for text, that's OK.

That said ~ I've not set up any other cellular phone to use a non-apple SMS.

And any reference to learn how to do that, would require me to study or 'search

for' Apple support site links, in the wild. The home page to the following link is

support.apple.com/guide/messages and that covers many details; I don't know.

• Set up iPhone to get SMS texts on Mac - Apple Support

https://support.apple.com/guide/messages/get-sms-texts-from-iphone-on-your-mac-icht8a28bb9a/12.0/mac/10.14

The above article covers reference to non-Apple generic SMS, also iMessage.

• Deregister and Turn Off iMessage - Apple Support

https://selfsolve.apple.com/deregister-imessage/

"To use Deregister iMessage, enable cookies in your browser and try again. ...

You may need to turn off iMessage if you are now using a non-Apple phone

and can't get SMS or text messages someone sends you from an iPhone."

And other links have secondary info linked. I'm not an expert; just a volunteer

here. Not compensated; not an Apple employee. And I've searched interwebs.

Default for non-iMessage phone users is SMS.

• SMS and MMS text messages - Apple Support

• Use Continuity to connect your Mac, iPhone, iPad, iPod touch, and Apple Watch - Apple Support

• Use Messages with your Mac - Apple Support

Good luck & happy trails!🌞🌎

All group participants have iPhone or something from apple ecosystem ?