Block Ban

Block Ban is a Paper plugin created to ban blocks from being placed in certain worlds, or the whole server. The configuration file looks something like this:

default-banned-message: "<red>You cannot place that block!</red>"

worlds:
  # This section is specific to the overworld. Please change if your overworld has a different name.
  world:
    # This is optional, the default banned message will be used if not specified here.
    banned-message: "<red>You cannot place that block!</red>"

    # Leaving this empty is the same as not including this world in the list.
    banned-blocks:
      TNT:
        banned-message: "<red>You cannot place TNT!</red>"

      # No banned message is specified here, so the world's message will be used.
      OBSIDIAN: {}

  # This section contains server-wide block bans.
  __server__:
    banned-blocks:
      TNT:
        banned-message: "<red>You cannot place TNT! In the overworld, this message will be overwritten.</red>"

A minimal version that only bans TNT server-wide would look like this:

default-banned-message: "<red>You cannot place that block!</red>"

worlds:
  __server__:
    banned-blocks:
      TNT: {}

Of course, you may want custom messages for each banned block. That is totally doable, and is why Block Ban should be your plugin for banning blocks. The provided example in the real configuration is more direct than this, and explains everything you need to know when banning blocks.