I recently try to add a file to my messenger via text message Samsung stock app and it would not allow me to even access Samsung stock messenger only Google Messenger and Facebook Messenger I'm not sure if this is a problem with the beta but I was always able to do it prior to the beta and I think I had the ability to do it before after the beta but not sure.
Size of the file you are trying to transfer determines whether file can be sent over Samsung Messenger or not. Samsung Messages follows SMS protocol on unlocked devices as most carriers do not support RCS on unlocked devices.
Google Messages on other hand use RCS and have much higher limit of file transfer capabilities.
