Hi Onoxin,
thanks for using MH UrbanMag (= child theme of MH Magazine lite).
What you could do (if you’re familiar with coding) is create a new custom child theme for MH Magazine lite based on MH UrbanMag, copy the file content-single.php from the parent theme to your child theme and delete this line of code in that file:
mh_magazine_lite_featured_image();
That will remove the featured image on posts, while still using the featured image for the thumbnails on archives and widgets.
As an alternative (in case you don’t want to touch code), the premium version of MH Magazine includes an option to disable the featured image on posts, as well as several other additional features, options and custom widgets to configure your website.
While using the premium version of MH Magazine, the MH UrbanMag child theme is no longer needed as you can configure the design and layout of MH UrbanMag by making use of the built-in options and custom widgets in MH Magazine (see theme demo).