I am using "Android Messages" (until recently called "Google Messenger") for SMS on my Moto G (3rd generation).
Works fine, except for sending images. It tries (Sending...) for a few minutes, and eventually tells me that it was not able to send.
I cannot discover where to get support for this app. I had used Textra in the past, and never had trouble sending images.
I would appreciate help, even if the only help is letting me know how to file a bug report.