With this super simple plugin players can send them into the bungeecord/velocity lobby by using the /lobby command. You can set the lobby server in the config.yml .
CAUTION: This is a Spigot/Paper plugin and doesn't work if you put it on the proxy server.
Features:

• Simple /lobby command that sends players to your BungeeCord lobby server
• Configurable server name (config.yml)
• Reload config with /lobbyreload

Permissions:

• lobby.reload (default: op)