mymodule.something.first:
  route_name: mymodule.something.first
  title: 'Do first thing'
  weight: -20
  appears_on:
    - entity.node.canonical

mymodule.something.second:
  route_name: mymodule.something.second
  title: 'Do second thing'
  weight: -20
  appears_on:
    - entity.node.canonical

mymodule.something.first:
  path: '/node/{node}/first'
  defaults:
    _controller: 'DrupalmymoduleControllerModuleController::first'
    _title: 'Do first thing'
  options:
    parameters:
      node:
        type: entity:node
  requirements:
    _permission: 'access content'
    _custom_access: 'DrupalmymoduleControllerModuleController::firstAccess'
    _csrf_token: 'TRUE'

mymodule.something.second:
  path: '/node/{node}/second'
  defaults:
    _controller: 'DrupalmymoduleControllerSubscriptionController::second'
    _title: 'Do second thing'
  options:
    parameters:
      node:
        type: entity:node
  requirements:
    _permission: 'access content'
    _custom_access: 'DrupalmymoduleControllerSubscriptionController::secondAccess'
    _csrf_token: 'TRUE'

public function dofirstthing(NodeInterface $node) {
    /* ... some logic ... */

    return $this->redirect('entity.node.canonical', ['node' => $node->id()], ['absolute' => TRUE])->send();
}