Talked with several players and we all have the same issue but have different setups. Has to be an issue within WC3 Reforged. None of us have this issue with any other games.
The flickering on the monitor is brief and usually random but tends to occur more if for some reason you alt tab or window out and come back to the game. Ive tried all settings known to man in game and in windows. Ive tried multiple video cards 980 and 3090. Ive tried multiple monitors. Nothing changes. All other games no issue.
In WC3 Reforged it will just flicker. Sometimes twice an hour, other times 10 times an hour. It is extremely brief and you wouldnt catch it unless your looking directly at the screen.
Difficult to diagnose unless you provide an easy way to reproduce the issue.
I have experienced flickering in WC3 in the past but in that case it was caused by the 8 light limit that classic graphics has. Units and effects with mobile light sources could potentially drown out the global illumination light source in a way that is unstable so result in the entire screen dimming every few frames as these dynamic light sources moved around.
I would hope Reforged graphics does not have this limit similar to how StarCraft II does not. It was my understanding that the limit arose from API limitations with fixed function (before programable shader) pipelines of D3D8 and OpenGL so should not be an issue for a D3D11 or later targeted renders made with programmable shaders.
the warcraft 3 engine pre-dates direct x 11. the engine is ancient, though not only used in warcraft 3. think it was used in war of the ring and battle realms. war of the ring was released by sierra so, how they got it is not difficult to figure out. liquid worked with sierra on it and that likely gave them access to the engine, enabling them to use it for battle realms… sorry for going off topic. my point is that old engines requires direct x 9 to work well. warcraft 3 initially ran on earlier versions of direct x. it ran in windows 98 after all, though i never tested it in 95. i did test it on mac os, though i am not sure what version it was.
Reforged development updated the graphics API to match current Blizzard policy of D3D11 minimum. It might still have optional D3D9 via command line but this is deprecated (not recommended to use, can be removed in future patches). All modern hardware runs D3D11 a lot better than D3D9 anyway to the point that people are creating D3D9 adapters for more modern APIs for better performance.
OpenGL. Fixed function pipeline (no shaders).
Now uses Metal, since OpenGL is deprecated (likely to be removed in future versions of MacOS). I do not think you can get Warcraft III to even run with OpenGL on MacOS.
based on the graphics quality i experienced on mac os, it looked more like software rendering than opengl. it was one of my father`s work macs, that he did his publishing work on. i used my original disc however to install it. i still have that, meaning that i can still run warcraft 3 on old hardware if i want. one of my teachers at school ran it on an intel hd gpu. think it ran a bit slowly.