I'm in Europe, and I'm doing it to the best extent that I can: no permissions allowed to whatsapp, no profile picture, no read receipts, no notifications, sending a standard message to all personal groups that 'lads, I'm moving to signal, ciao'.
Beyond that, I will not entertain personal messages on whatsapp, only work related. Each new person will be greeted with "Do you mind awfully if we use Signal?" Does this come off as self-important? Sure. But it helps that I don't care too much if it does. I had the same attitude quitting FB and Twitter too, I just don't need people that much. I don't have a 100 friends anyway. I have like 15 that I really want to keep in touch with. Those 15 will understand.