It isn't harder to use than Whatsapp. It's actually simpler, because it has less useless bells and whistles.
All you need to do is convince them that it's for their good, if they can agree on that then the technicality isn't difficult.
All you need to do is convince them that it's for their good, if they can agree on that then the technicality isn't difficult.
I suspect one of the most difficult to address is getting it to successfully evade the random vendor-built aggressive battery saving settings in Android. WhatsApp is usually whitelisted from those so "just works". If you don't do similar things for Signal, it will stop picking messages up/notifying you after a day or two of inactivity.
Unfortunately, that leaves me with ... nothing to recommend people switch to.
Whatsapp allows media from specific chats to be auto saved to photos. It is a very important feature, not sure how these aren’t making the priority bar.