I was really disappointed when Signal went away from being used as an "everything" messenger, including regular SMS. I onboarded all my family and now because it's not a default messenger, nobody is using it.
- Signal. high priority channel, checked daily
- $PrivacyHazardApp. low prio, checked with steadily increasing intervals.
Make sure you communicate those intervals in advance, have them in the footer of every message you sent on $PrivacyHazardApp. Average Joe needs lots of patience and lots of education.