Bug Terrain Is Broken 2018/2019

Unity Terrain 2018.4.12f1, basically, i have 2 textures, and you can see few issues:
1. there is little to no blending
2.these weird, edges, as i paint grass on the ground, keep showing up, and i am unable to get proper blending.


i tested out, with unity 2017.4.34
and well, this is the result i get, i can blend, properly, even with like 3 textures.

so like, does anyone, have any idea? is there a fix? i tried 2019, but no avail.

not being able to use, any terrains functionality is just, painful, and limiting for some projects.

i am using linux mint 19.2
I5
16GB Ram
AMD 7970 Series
i tried, setting build target to Linux, to Windows, To Android, but no difference at all.
i tried changing from Gamma to Linear, there was also, no change at all.

please note: exporting terrain from 2017 to 2018, the terrain then would look fine in unity 2018
but, modifying the terrain in unity 2017, anything 'new' or any new change i add, is broken, like in the screenshot.

 

i am still facing the same problem, i just thought, this video, might help others, understand the problem more, note i tried all brushes, i also tested with different textures, the ones i use in the video are the ones from unity standard assets.

anyone else facing similar issues?
extra note, the terrain in this video, is a standard one, i simply, right clicked, chose 3D Object then chose terrain and added these layers, this is literally an empty project, with only the standard assets in it.

 

If you can use the 2019.3 beta, it is the best version for Linux until now, because it's the first official release for Linux, and works ok for me.