I've been using data-only plans since 2015 combined with voip.ms VoIP numbers (for Toronto and SF). This means I could travel and pop in a prepaid SIM card whenever I went anywhere and not have any problems using data-based messaging services (Signal/WhatsApp/iMessage).
As of this year I ditched my T-Mobile prepaid data SIM and exclusively use prepaid eSIMs (esimdb.com has a great comparison, but Nomad makes it very easy with their app). So I still have to "swap sims" but it's all done on the iPhone itself, no need to bring a sim ejector/paperclip.
What's really funny is that last week my eSIM ran out (I forgot to top up) and my 16 Pro connected to the satellite network (since it assumed no service was available I guess?), where I was able to use iMessage (in the limited way (to individuals, not groups)).
How exactly are you using iMessage with your VoIP number? I thought it requires a valid SIM card to register the number. Also, aren't SMS, MMS media, and MMS groups super finicky with VoIP services?
As of this year I ditched my T-Mobile prepaid data SIM and exclusively use prepaid eSIMs (esimdb.com has a great comparison, but Nomad makes it very easy with their app). So I still have to "swap sims" but it's all done on the iPhone itself, no need to bring a sim ejector/paperclip.
What's really funny is that last week my eSIM ran out (I forgot to top up) and my 16 Pro connected to the satellite network (since it assumed no service was available I guess?), where I was able to use iMessage (in the limited way (to individuals, not groups)).