After reading Jmix 2.x documentation on
multiSelectComboBox and Instance Container i invent this solution,
i like to share.

Following the steps I did to create the DB->GUI and GUI->DB interaction

Define enumeration in order to have have the choices we need

// www.data-ware.it
public enum it.data-ware.ValueEnum implements EnumClass<String> {
    32BIT("32BIT"),
    64BIT("64BIT"),
....
}

Place the component on ““Detail”” view of the Entity

<formLayout id="form" dataContainer="nameDc">
                    <multiValuePicker id="architectureValuePicker" label="Architecture">
                        <actions>
                            <action id="select" type="multi_value_select">
                                <properties>
                                    <!-- mind the gap --> 
                                    <!-- we are handling ValueEnum Object --> 
                                    <!-- mind the gap --> 
                                    <property name="enumClass" value="it.data-ware.example.entity.ValueEnum "/>
                                </properties>
                            </action>
                            <action id="clear" type="value_clear"/>
                        </actions>
                    </multiValuePicker>
</formLayout>

On the Detail View code form we need to handle events from Jmix
public class CustomEntityDetailView extends StandardDetailView {
}

First, inject the component valuePicker, defined on the xml form

@ViewComponent
private JmixMultiValuePicker<Object> valuePicker;

Then subscribe the onReady event in order to fill the component values to UI component

// www.data-ware.it
@Subscribe
public void onReady(final ReadyEvent event) {
    // ...
    final String architecture = getEditedEntity().getArchitecture();

    // ...
    final String[]          architectureParts     = architecture.split(";");
    final ArrayList<Object> valuePartsEnum = new ArrayList<>();

    // ...
    for (String architecturePart : architectureParts) {
        // mind the gap
        // from string to Enum 
        final ValueEnum item = ValueEnum.fromId(architecturePart);
        valuePartsEnum .add(item);
    }

    // ...
    valuePicker.setValue(valuePartsEnum );
  }

Finally subscribe the onBeforeSave event to get component values from UI and set it on Entity field to allow Jmix to save it.

@Subscribe
public void onBeforeSave(final BeforeSaveEvent event) {
    // ...
    getEditedEntity().setArchitecture("");

    // set empty field and exit
    if (!architectureValuePicker.isEmpty()) {
        // ...
        final Collection<Object> collection = valuePicker.getValue();

        // ...
        final StringBuffer architectureParts = new StringBuffer();

        // ...
        collection.forEach((temp) -> {
            architectureParts.append(temp).append(";");
        });

        // ...
        architectureParts.setLength(architectureParts.length() - 1);
        final String architecture = architectureParts.toString();

        // ...
        getEditedEntity().setArchitecture(architecture);
    }
}