https://bugs.winehq.org/show_bug.cgi?id=41166
--- Comment #12 from Sveinar Søpler cybermax@dexter.no --- There is no "official patch" stating that OpenGL is removed from the game... cos it isn't. You can still use the "OpenGL hidden option" (i call it hidden, cos its not a selectable option in-game like DX9 and DX11 is, but have to manually edit the config file), and the game will start with OpenGL... Its just unplayable and contains garbled graphics.
The two links that Jason posted is the "confirmation" that Blizzard is not actively working on OpenGL for Windows anymore, and thus must be considered "not available".
Official requirements listed here: https://eu.battle.net/support/en/article/76459
Windows XP no longer supported, but it does not spesifically state what version of DirectX you need. DirectX 9 is still supported and run, but is sadly bugged with missing ground textures in many places (Spell effects and the likes). They (Blizzard) has not said anything "official" about that tho, other than that it was a similar bug for Mac client (Metal/OpenGL), and it has been somewhat fixed from what i gather.
I don't know technically if the OpenGL "hidden option" exist because it is needed for the Mac client, or if it will be removed in the future tho. The DX9 option is still available, but when people ask for support regarding this the answer from the support staff is always "Upgrade your graphics driver to a DX11 compatible one and use that" more or less.