"Or even, how can I just remove or hide the Users (with Users and Groups) completely?"
So, we have SonataUserBundle and our AppBundle.
In both of them we have User and Group Entity. And we don't want to use entities from sonata - we just extend them. But SonataUserBundle has already had the UserAdmin and GroupAdmin classes inside.
That's why, after installing SonataUserBundle in the admin menu appear two services:

As you know, every sonata admin class we declare in the services.yml file.
In SonataUserBundle we have another files, which sonata developers declare services in. In case of using doctrine orm we should look at admin_orm.xml file, which lies in this path:
vendor/sonata-project/user-bundle/Resources/config/admin_orm.xml
Inside the file we can find the declaration of the admin services - UserAdmin and GroupAdmin:
<?xml version="1.0" encoding="UTF-8"?>
<container xmlns="http://symfony.com/schema/dic/services" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://symfony.com/schema/dic/services http://symfony.com/schema/dic/services/services-1.0.xsd">
<parameters>
<parameter key="sonata.user.admin.groupname">sonata_user</parameter>
<parameter key="sonata.user.admin.label_catalogue">SonataUserBundle</parameter>
<parameter key="sonata.user.admin.groupicon"><![CDATA[<i class='fa fa-users'></i>]]></parameter>
</parameters>
<services>
<service id="sonata.user.admin.user" class="%sonata.user.admin.user.class%">
<tag name="sonata.admin" manager_type="orm" group="%sonata.user.admin.groupname%" label="users" label_catalogue="%sonata.user.admin.label_catalogue%" label_translator_strategy="sonata.admin.label.strategy.underscore" icon="%sonata.user.admin.groupicon%"/>
<argument/>
<argument>%sonata.user.admin.user.entity%</argument>
<argument>%sonata.user.admin.user.controller%</argument>
<call method="setUserManager">
<argument type="service" id="fos_user.user_manager"/>
</call>
<call method="setTranslationDomain">
<argument>%sonata.user.admin.user.translation_domain%</argument>
</call>
</service>
<service id="sonata.user.admin.group" class="%sonata.user.admin.group.class%">
<tag name="sonata.admin" manager_type="orm" group="%sonata.user.admin.groupname%" label="groups" label_catalogue="%sonata.user.admin.label_catalogue%" label_translator_strategy="sonata.admin.label.strategy.underscore"/>
<argument/>
<argument>%sonata.user.admin.group.entity%</argument>
<argument>%sonata.user.admin.group.controller%</argument>
<call method="setTranslationDomain">
<argument>%sonata.user.admin.group.translation_domain%</argument>
</call>
</service>
</services>
As you can see here the ids of our services:
sonata.user.admin.user
sonata.user.admin.group
The simplest method to overwrite them is to create the same services (I mean we will use this ids ) in our services.yml file.
Yes, you can have an argument with me, that this method is stupid, but as I said it's not the only one.
So Sonata services in OUR services.yml will looks like this:
sonata.user.admin.user:
class: "%sonata.user.admin.user.class%"
arguments: [~, "%sonata.user.admin.user.entity%", "%sonata.user.admin.user.controller%"]
tags:
- { name: sonata.admin, manager_type: orm, group: "%sonata.user.admin.groupname%", label_catalogue: "%sonata.user.admin.label_catalogue%", label: "users", icon: "<i class=\"fa fa-users\"></i>" }
calls:
- [ setUserManager, [ "@fos_user.user_manager" ] ]
- [ setTranslationDomain, [ "%sonata.user.admin.user.translation_domain%" ] ]
sonata.user.admin.group:
class: "%sonata.user.admin.group.class%"
arguments: [~, "%sonata.user.admin.group.entity%", "%sonata.user.admin.group.controller%"]
tags:
- { name: sonata.admin, manager_type: orm, group: "%sonata.user.admin.groupname%", label_catalogue: "%sonata.user.admin.label_catalogue%", label: "groups" }
calls:
- [ setTranslationDomain, [ "%sonata.user.admin.group.translation_domain%" ] ]
Now you can update the admin dashboard and see, that nothing have happened. But the our purpose was to disable this service from our dashboard and menu. Let's do the trick. Add
show_in_dashboard: false
tags:
- { show_in_dashboard: false, name: sonata.admin, manager_type: orm, group: "%sonata.user.admin.groupname%", label_catalogue: "%sonata.user.admin.label_catalogue%", label: "users", icon: "<i class=\"fa fa-user\"></i>" }
to the declaration of this service in services.yml.
Therefore our services will look like this:
sonata.user.admin.user:
class: "%sonata.user.admin.user.class%"
arguments: [~, "%sonata.user.admin.user.entity%", "%sonata.user.admin.user.controller%"]
tags:
- { name: sonata.admin, manager_type: orm, group: "%sonata.user.admin.groupname%", label_catalogue: "%sonata.user.admin.label_catalogue%", label: "users", icon: "<i class=\"fa fa-user\"></i>", show_in_dashboard: false }
calls:
- [ setUserManager, [ "@fos_user.user_manager" ] ]
- [ setTranslationDomain, [ "%sonata.user.admin.user.translation_domain%" ] ]
sonata.user.admin.group:
class: "%sonata.user.admin.group.class%"
arguments: [~, "%sonata.user.admin.group.entity%", "%sonata.user.admin.group.controller%"]
tags:
- { name: sonata.admin, manager_type: orm, group: "%sonata.user.admin.groupname%", label_catalogue: "%sonata.user.admin.label_catalogue%", label: "groups", show_in_dashboard: false }
calls:
- [ setTranslationDomain, [ "%sonata.user.admin.group.translation_domain%" ] ]
After this trivial manipulations Sonata services will completely disappear from your Dashboard.