The Apple TV series Mythic Quest had an episode in which the game found it had an extreme right wing problem. Their solution was to corral the right wingers in a server where they could shout at each other and fight as much as they wanted without bothering other players.
The Fediverse, running, as it does, largely on free software, came about in part due to Twitter and other platforms' unwillingness or inability to deal with an extreme right wing problem. However, as it's free and open source software, the bad actors were also free to create their own instances and interact. The response was filtering, blocking and defederation.
If you run a Mastodon, or other Fediverse social media instance, even if it's for yourself, it's one of the most powerful tools you have. You can filter hashtags, users and whole instances both personally and globally.
Lists have developed over the years along with the tools to apply them, but they have often been personal efforts. The hashtag #fediblock can also be used, but it's something of a blunt instrument and is too easily hijacked for personal opinions and even feuds.
The current attempt to deal with this in an effective way is the Oliphant.social blocklist files, created through a consensus of ten of the most active fediverse instances This produces a collection of blocklists that can be applied as an administrator sees fit. Follow the instructions there to download, maintain and apply them. At the moment I apply the Tier 0 blocklist.
In addition, Ro Iskinda's The Bad Space collects the most commonly reported bad actors and new ones that appear, and can be used with an API to check if you encounter a doubtful user or instance.