You can view all of a person's posts filtered by hashtag by adding "/tagged/" to the end of their public profile address, then adding the hashtag.
For example, here is a link to all of switching.social's posts tagged #MastoTips:
https://mastodon.at/@switchingsocial/tagged/mastotips
This can be very useful for artists wanting to link to a portfolio, or writers wanting to link to articles about a topic.
You can also add these to your public profile page by going to Preferences > Edit Profile > Featured Hashtags