Comment 8 for bug 1904599

Thanks for the clarification Alex! The problem in this case was actually related to a missing parameter for the mysql router and that was the reason why the installation was failing. There is a db-router parameter that has to be defined in order to assign the mysql router and the inno db cluster to a specific network. This is already documented in https://bugs.launchpad.net/charm-mysql-router/+bug/1881171

[...]
services:
  keystone-mysql-router:
    charm: cs:~openstack-charmers-next/mysql-router
    bindings:
     db-router: *internal-space
  nova-mysql-router:
    charm: cs:~openstack-charmers-next/mysql-router
    bindings:
     db-router: *internal-space
  glance-mysql-router:
    charm: cs:~openstack-charmers-next/mysql-router
    bindings:
     db-router: *internal-space
  neutron-mysql-router:
    charm: cs:~openstack-charmers-next/mysql-router
    bindings:
     db-router: *internal-space
  dashboard-mysql-router:
    charm: cs:~openstack-charmers-next/mysql-router
    bindings:
     db-router: *internal-space
  heat-mysql-router:
    charm: cs:~openstack-charmers-next/mysql-router
    bindings:
     db-router: *internal-space
  placement-mysql-router:
    charm: cs:~openstack-charmers-next/mysql-router
    bindings:
     db-router: *internal-space

[...]

 mysql-innodb-cluster:
    charm: cs:~openstack-charmers-next/mysql-innodb-cluster
    num_units: 3
    bindings:
      "": *oam-space
      cluster: *internal-space
      # added shared-db to db-router
      db-router: *internal-space
      shared-db: *internal-space
    options:
      source: *openstack-origin
      innodb-buffer-pool-size: 512M
      wait-timeout: 3600
      enable-binlogs: True
      max-connections: *mysql-connections
    to:
    - lxd:1
    - lxd:2
    - lxd:3