I just built a new computer: Radeon Rx 5700, MSI Pro Carbon AC motherboard, and Ryzen 7 cpu. The monitor (ViewSonic XG monitor with freesync connected via displayport) will flicker often when running games, and will either just be black or say no signal. When I have a second monitor, it does this too. When I load up League of Legends this problem is almost guaranteed, with launcher glitches and entire computer not responding correctly when starting a game. The computer runs better than my last, but this problem is very prevalent and annoying.
I also have this issue with LoL if I use any drivers after 19.8.2. I would love to update my drivers, but due to this issue with league I'm always hesitant.
With 19.8.2, I still have stutters and periodic frame drops, but at least I can actually play the game.