You can automatically hide posts containing certain words, phrases, hashtags or emoji by using Mastodon's Filters feature. Filters can be set to either hide posts completely or hide them behind a content warning.
Lots more info on how to use Mastodon's filters in the guide at:
➡️ https://fedi.tips/filtering-your-timeline-to-hide-posts-on-mastodon
Hopefully this guide covers all the most commonly asked questions about filters. If there's something missing, please let me know in the replies 🙂