I use mine on a sofa (for gaming, even!), but I get around the issue a bit by having a pad under the laptop. It’s literally just a hard plastic board with a beanbag attached underneath, I think I got it from IKEA. It isolates the laptop a bit from dust and improves airflow + lets it heat up without burning my knees + the one I have is just large enough that I can also use my wireless mouse on it when I push my laptop to the left.