Samsung Galaxy S8 Not Sending MMS via WiFi Since Upgrade to Android 9.0

[Android Central Question]

I've had Mobile Date turned off since I got the phone 2 years ago (to save on data charges) and every since my phone updated to Android 9.0, MMS messages will not send, or be received, via WiFi. I have to turn Mobile Data on for MMS to send/receive even when connected to WiFi. All other features & functions (email, etc.) still work perfectly fine with Mobile Data turned off when I'm connected to a WiFi AP

 

[Elnlou]

I have the same issue. After update to Pie 9 the text app that worked perfectly sending and receiving MMS texts over wifi (data off) was switched to a native app. This native app no longer allows MMS texts to be sent or received. My provider is Boostmobile. I spoke to Samsung tech support who tried to help but the fix needs to come from Boostmobile. Boostmobile says Samsung needs to fix it. I believe Boostmobile stopped supporting MMS over wifi when they implemented the RCS/chat technology with the Pie 9 update.