switching.socialYou can already do this on Mastodon by using the following URL:
(Public Profile URL) /tagged/ (hashtag you want to filter)
For example, if I want to search switching.social's account for the hashtag "Alternatives", the URL looks like this:
Bobinas P4G is a social network. It runs on GNU social, version 2.0.1-beta0, available under the GNU Affero General Public License.
All Bobinas P4G content and data are available under the Creative Commons Attribution 3.0 license.