So the insider builds have trouble with transparency, and I can't be bothered to move back. In a couple of days most people will get thrown on this build anyway, so I messed around a bit to make TH look a bit better for me.
There's just a couple of elements that use transparency, so I simply disabled them all.
config > ui_default > ui_default_main.xml, set minimap_enabled to 0. You can still press tab to check which way the map goes, but no more black on the minimap!
plugins > default > ResourceOverGlobePlugin.cs, comment out line 155 (place // before glowTexture.draw(uiRect etc.).
plugins > default > inventory > InventoryAndStashPlugin.cs, set NotGoodDisplayEnabled to false (line 43).
plugins > default > items > PickUpRangePlugin.cs, set Enabled to false (line 15).
You lose pretty much no functionality, and get rid of the black crap on your screen. Looks something like this: https://i.imgur.com/hGm6gRY.jpg