The American Speech-Language-Hearing Association (ASHA) has you covered. This section of their website lists all of the signs and symptoms that are related to language comprehension.
My son had language comprehension challenges, and as a parent, I felt overwhelmed. Knowing these signs and symptoms would have helped me understand what was going on when he was a young child.
As I now teach the Language Arts classes for the Early Childhood Education program at Georgian College, we spend most of our time on learning about effective strategies for supporting children's language comprehension. If you would like to play a fun game, click on this interactive website I use in class. Click on "Click-a-Sticks" at the top, and learn about all of the ways we can support language comprehension with young children.
Kovack, M. (2019). Experiences in Language Arts: Preschool Literacy. [Website]. Retrieved from https://marthakovack.wixsite.com/preschoolliteracy