Steps to reproduce the issue

Create a subform field and use a fancy-select inside it.

The code is used is:

 <field
                    name="sorting_rules"
                    type="subform"
                    label="Sorting rules"
                    layout="joomla.form.field.subform.repeatable-table"
                    icon="list"
                    multiple="true"
            >
                <form hidden="true" name="list_sorting_rules" repeat="true">
                    <field
                            name="name"
                            type="list"
                            label="Select"
                            multiple="false"
                            layout="joomla.form.field.list-fancy-select"
                            required="true"
                    >
                            <option value="a">A</option>
                            <option value="b">B</option>
                            <option value="c">C</option>
                            <option value="d">D</option>
                            <option value="e">E</option>
                    </field>
                </form>
            </field>

You can inject that in any component's config.xml or a menu item's xml to check it.

Expected result

The drop-down options to be visible.

Actual result

Not visible

System information (as much as possible)

Joomla 5.1.2