Yes, you can monitor hashtags with Mention!
This possibility is available for Twitter and Instagram. It's even a recommended practice to input your keywords both ways, for example: #Mention and Mention. This helps ensure that all mentions get brought in.
Concerning Facebook, we don't have this hashtag notion, so if you add a normal keyword in your request or query, you will get also the hashtags that match with this keyword.
★ In Basic Alerts
In Basic Alerts, you can add your hashtag as a keyword.
★ In Advanced Alerts
The Boolean Query lets you monitor hashtags as a keyword too. The first character of a keyword can be # or @, if you want to search for hashtags or handles in Twitter or Instagram.
👉 Know more about the Boolean Operators here.