Short answer: any hardware capable of GLES 3. GLES 2 is also supported but I would not recommend except for games for low-end smartphones.
Long answer: it is to you to fix such requirements. A game engine cannot fix such requirements as they are dependent on the game your making. With Godot you can make 2D 16bits retro game or a full blown 3D games with tones of effects. As you can imagine the requirements between the two will bet very different. In addition, for example, with Godot you are also able to program your own AI which can dramatically increase CPU usage. As you have probably understood by now, only you know the minimum requirements.