#FediTip for instance admins: On #Mastodon you can #FediBlock the base domain to block its subdomains as well.
For instance, blocking dumpsterfire.social will work for the subdomains pl.dumpsterfire.social, ak.dumpsterfire.social and any other subdomain they might spin up in the future.
This works even if dumpsterfire.social itself is not a federated instance and doesn't show up as a choice in search. Simply click the "Add new domain block" button in the upper right of the federation menu, enter dumpsterfire.social and do your thing.
Alternately you can search first and then click on the add new block button to both verify the domain and auto-populate the domain name field.
Particularly for dumpster fires that only have instances on subdomains, this gives you peace of mind and saves you the labor of tracking down new subdomains. I have seen instances use wildcard asterisks * for blocks, which do NOT work at least on mainline Mastodon/Hometown and should be replaced by base domain blocks.