*Update 06.10.2025
For those who are still having the problem, despite recent Opera (Stable) updates, I found a solution that works perfectly after testing three different graphics cards (AMD).
These are simply driver issues from AMD (25.5.1 & new 25.6.1) (WHQL) (Shi drivers...see on Reddit)*
Test with v. 25.3.1 & 25.4.1 WORKS perfectly (0 whites screen after fullscreen a few minutes)
Cards used:
- RX 6600
- RX 9070 XT
- RX 580