For context the phone I have now is a Nokia 8.3 5G
The following were said previously to work for textnow service even without wifi on their free plan data sim. These are my experiences using the service a little bit more on my primary phone.
You can still send MMS flawlessly. I assume this is very much intended.
Facebook apps don't work
Google Voice can notify you that you received a text or voicemail but you cannot read either of them
You can still ask Google a question but it is slow.
My logic is the newer the phone that comes out the more glitches will be patched up. YMMV