I just say "can we use Signal? It's super secure." And people generally are fine to use Signal. They don't use SMS because it's expensive and many that own an iPhone in countries where Android dominate don't use iMessage because, well, few around them use iPhone and the interface (i.e., the phone number) doesn't really tell them that they won't get charged for a text message.
I've posted up in many countries, and it's rarely a show stopper.
I just say "can we use Signal? It's super secure." And people generally are fine to use Signal. They don't use SMS because it's expensive and many that own an iPhone in countries where Android dominate don't use iMessage because, well, few around them use iPhone and the interface (i.e., the phone number) doesn't really tell them that they won't get charged for a text message.
I've posted up in many countries, and it's rarely a show stopper.