load_block_on_ajax-8.x-1.0/load_block_on_ajax.routing.yml

load_block_on_ajax.ajax:
  path: '/load-block-on-ajax/{block_machine_name}'
  defaults:
    _controller: '\Drupal\load_block_on_ajax\Controller\LoadBlockController::loadBlock'
  methods:  [GET]
  requirements:
    _permission: 'access content'