Apple makes brightness shortcuts simple and consistent across all MacBooks and iMac keyboards:
Press Windows Key + X , then tap B (or select Mobility Center) to find a brightness slider. macOS Brightness Shortcuts
Hold Option + Shift + F1/F2 to adjust brightness in smaller increments for finer control.
Most Windows laptops use a combination of the key and a specific top-row function key (F1–F12) marked with a "sun" icon.