Hi,
I switched from Divested build to a regular vanilla and stable openwrt 19.07. I just changed the mwlwifi driver to the last available kaloz version that @eduperez precompiled and that's it.
I have not had any samsung 8 disconnects or any other major symptom. Wifi is stable, speeds are great and I can have static leases without disconnects. Ofc being an official 19.07 it does not have the security tighten as with Divested and it is still running on the old switch sw instead of DSA.
I have a hunch that the S8 disconnects has to do more with DSA builds rather than the mwlifi. But I have no clue how to prove it.
Hope it helps