The "node discovery" feature was added to implement overlay networks with an external k/v store
https://docs.docker.com/engine/reference/commandline/dockerd/#node-discovery

With swarm "standalone" being in maintenance mode, and SwarmKit providing all functionality to create overlay networks (which could be used for standalone swarm if created with the --attachable option), we should deprecate this feature, and remove it.

• deprecate/remove --cluster-advertise, --cluster-store , --cluster-store-opt flags from dockerd CLI
  • remove options from libnetwork [do not merge] remove "discovery" options libnetwork#2521
  • vendor libnetwork changes and remove local discovery packages Remove deprecated host-discovery and overlay networks with external k/v #42247
  • Deprecate classic Swarm and overlay networks using external k/v stores docker/cli#2448 Deprecate classic Swarm and overlay networks using external k/v stores
  • hide/deprecate flags and print warning Deprecate '--cluster-xx' options and add warning #40510 "Deprecate '--cluster-xx' options and add warning"
  • Add warnings for deprecated "cluster" functions, and deprecate API fields Add warnings for deprecated "cluster" functions, and deprecate API fields #40614
    • Add warning about deprecated "cluster" options to "docker info"
    • API: deprecate /info "ClusterStore" and "ClusterAdvertise" fields
  • remove equivalent options from daemon.json (or produce error)
• update reference docs
  • remove flags from dockerd command line reference
  • remove flags from dockerd (8) man page
• Remove the Overlay networking with an external key-value store documentation

The following flags will be removed/deprecated on the dockerd daemon:

      --cluster-advertise string                Address or interface name to advertise
      --cluster-store string                    URL of the distributed storage backend
      --cluster-store-opt map                   Set cluster store options (default map[])

(this is just a placeholder to start the discussion, I'll add more information about things to change)