Hey, thanks for your answer!
I realized that because I use Elementor, the option to set the featured image is moved there. When you’re viewing a post page with Elementor, it’s available in the settings on the lower left.
Hey, I forgot to mention that I’m using a child theme I created from the latest version of Neve with the Child Theme Configurator plugin.
I switched back to the “mother” Neve theme and tried copying the code I mentioned above in that theme’s functions.php file but it still hasn’t fixed my issue.