Turn off the Xbox Game Bar , Discord Overlay , and background recording (ShadowPlay/ReLive), as these frequently conflict with the game's engine.
The most immediate way to stabilize performance is by adjusting in-game settings to match your hardware capabilities: Diablo Immortal Fps Drop Fix Reduce Lag & Shut...
A known community fix involves deleting the 'LocalData' folder within the Diablo Immortal installation directory. This clears potentially corrupt cache files that cause stuttering. Turn off the Xbox Game Bar , Discord
Enable Hardware-accelerated GPU scheduling in Windows settings and ensure your Power Plan is set to "High Performance". Turn off the Xbox Game Bar
Turn off Post-processing and Anti-aliasing (or set to Low) to gain significant performance headroom and improve image clarity.