I have problems both sending and receiving mms with my Fairphone 3.
I live in Norway and the service provider is Onecall.
I can send and receive emails, browse internet, send-receive, call and videocall in whatsapp both using wi-fi and mobiledata.
The mms sometimes function and sometimes not. Its just random and does not follow any pattern that I am able to detect.
I like the mms function and would be happy to see it work.