*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)
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