Mastodon supports actual real search now! This is great to find interesting people and content from all over, even when people don't tag post. To be sure people can find _your_ public posts, opt in (your server has to be on Mastodon 4.2 or higher).
Setting in your Mastodon settings under "Public profile" > "Privacy and reach". Don't forget to hit the save button on the bottom of the page.