Give them 2 channels, be clear about your terms of service and that your intent is to become exclusively available on Signal after one year:

- 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.