My wife recently got her entire extended family to use Signal. She has always refused to use WhatsApp. They all love Signal now, and use it all the time. However, this was during a family crisis.
During the Covid lockdowns, many companies I know used Signal as their preferred non corporate communication platform over WhatsApp... But again, that was a crisis.
It seems to be difficult to dislodge people from their preferred platforms without some kind of external driver to adopt it.
