Pinterest has stated that using hashtags is completely optional and won’t much affect the reach of a pin. In fact, you’ll only get hashtag suggestions when creating a new pin in the mobile app. Suggestions are no longer available on the desktop version as of Sept. 2021.  The keywords that you use in the description majorly help find users to discover your pins. If you must, include 2-3 relevant hashtags at the end of your description. You can go up to 10 but don’t stuff more than that.