I honestly doubt this will be of any help to you. I had issues with my ryzen 2500u vega 8 APU laptop when i first got it back in december with ubuntu 18.10. I tried building a new kernel for it, and grabbing ppa's with update stuff, but the performace was just horrendous, black screens, flickering, green/purple lines that would run horizontally across the screen. I honestly thought it was a hardware issue, sent it back into HP. they checked it out and it was working normally. when i got it back, i installed the testing branch of ubuntu (what will become 19.04) and i am not sure what was in there, but all my problems went away. it runs like a champ now. added a better 2x8gb ddr4 2400 kit to it, put in a sata 3 m.2 drive, and the thing is a beast now. doesn't play very many games well, as the vega 8 isn't really a strong gpu, but it is better than the iGPU found on intel cpu's.