I just found this website today and installed the 6.4.4 version from this thread on my DuraXV Extreme E4810. It works fine for me. I copied the APK through OpenMTP, and then opened the APK on the phone to install it (Dev mode needed to be on to allow unknown sources). When I first opened it it kept crashing right away. I started pressing the middle button repeatedly and quickly each time I opened the app. That would close the crash window and the Message+ permissions request would then show. After a few times of allowing the various permissions, it now runs perfectly as the default messaging app.
It doesn't replace the Messages app. Message+ is located in Settings-Business Tools-Messages+. I set one of the programmable keys to open it.