Greasy Fork is available in English.
Tells YouTube that your browser only supports videos at 30FPS or less, which switches all 60FPS videos to 30FPS and allows old computers to watch high-resolution videos without stutter!
< Отзив за Disable YouTube 60 FPS (Force 30 FPS)
Idk why I haven't look for that script til now. And yes, it works 👍💯