The way Twitter users dealt with #DM #spam was to block DMs from non-followers. There are settings with similar effect on Facebook.
You can also do that on #Mastodon.
THIS IS NOT A HACK. It's literally why the feature exists. Use it. Maybe instead of banhammering the largest single instance on the #Fediverse.
The problem with this setting as compared to Twitter, is that on twitter blocking DMs from non-followers removes the option to DM the person entirely.
The "Block direct messages from people you don't follow" option on Mastodon removes your ability to receive those DMs, but doesn't give any notification to the user sending that the message won't be received or that they can't send one.
It's still a useful option, but can cause people to wonder why DMs are going unanswered.
FeralRobots
High intensity squirrel 🏳️⚧️