Does this sentence include an abstract noun the people were at meeting hall to protest?

Yes, the sentence "The people were at the meeting hall to protest" includes an abstract noun.

The abstract noun is "protest".

Here's why:

* Abstract nouns represent ideas, qualities, concepts, or states of being.

* Protest is an idea or action expressing disapproval or opposition.

While "meeting hall" is a concrete noun, "protest" is an intangible concept.