Glass and Mirror materials don’t have any texture within (they are plain pure materials), so i cannot disable mipmaps nor sRGB. Let me know if i’m wrong, I’m still a rookie.
Wow, I hope is not a limitation, but as far as you have tried to find a solution and you couldn’t, I’m a bit worried. There’s no way UE4 can be used for archviz without this feature. If i find a way to solve it of course I’ll let you know. Keep on trying different options but quite dissapointed about it.