Hi Yasmine.hs,
Thank you for reaching Microsoft Community. We appreciate for sharing your concern to us.
Regarding the possible negative effects of utilizing a thermoplastic polyurethane keyboard cover on a Surface Laptop 4, I was unable to locate any particular information. TPU-Clear, on the other hand, is a chemically improved plastic that is renowned for having qualities like greater hardness, flexibility, and scratch resistance. Additionally, it serves as a screen protector material.
In general, it’s important to keep your Surface Laptop clean and well-maintained to prevent any damage. Microsoft recommends using a soft lint-free cloth dampened with a little bit of mild soap and water, or screen wipes, to clean the touchscreen and keyboard frequently. They also advise keeping your Surface covered when you’re not using it. For more details, see Clean and care for your Surface - Microsoft Support.
If you are concerned about potential damage, you may want to consider removing the keyboard cover before closing the laptop lid.
Kind regards,
Lavenia