Mysql Innodb cluster does not show mysql server instances in Mysql shell
The unofficial docker innodb cluster manual does not use MySQL Shell to set up and configure the MySQL InnoDB cluster.

If you want/need to use the MySQL Shell to manage your InnoDB cluster then you must "adopt" the running Group Replication group. To do so, use the adoptFromGr option of dba.createCluster():

dba.createCluster("testcluster", {adoptFromGr: true})


For more information, please consult the official userguide:

https://dev.mysql.com/doc/refman/8.0/en/mysql-innodb-cluster-from-group-replication.html

Cheers,

Miguel