After reading a hundreds of posts on this forum i'll try to ask again about this problem.
Lenovo Z50-75 notebook
APU AMD FX-7500 with Radeon R7 integrated and R7 260DX discrete graphics.
Before the 1903 may update I've used this notebook since Win10 1511 installing every update without any problems with OS or drivers. After the installing this update I've received this problem: black screen before the login into OS or black screen stuck on screen with white dots. Previous driver, which should be transferred into updated OS was Radeon Adrenaline edition from october 2018. (it doesn't matter which version, I hope). After the update I received infinite black screen. And sure, safe mode didn't work on this try, because system did'n configurate properly after the update. OK, I tried to complete fresh installation. It was successful, except one moment - After the first reboot since AMD Driver installation (basic AMD from 2015\Adrenaline 19.6.1\19.6.2\19.4.3\ - 4 fresh OS installations attempts) I received in device manager message that "This device was stopped" with error code 43 on integrated R7. This problem get only in 1903 update and solved after rollback to 1809 update. Maybe AMD takes all information about this problem and try to investigate this problem together with Microsoft? (First posts with this problem start since the end of May). Is there any solutions at the moment other than rollback to last OS update?