Steps to reproduce

1. Install clean eZ Platform EE v2.2.2
2. Configure it as follow:
   ezplatform.yml

   siteaccess:
           list: [site, fr, admin, mybo]
           groups:
               site_group: [site, fr]
   
               # WARNING: Do not remove or rename this group.
               # It's used to distinguish common siteaccesses from admin ones.
               # In case of multisite with multiple admin panels, remember to add any additional admin siteaccess to this group.
               admin_group: [admin, mybo]
           default_siteaccess: site
   

   and

   ezplatform.yml

           admin_group:
               cache_service_name: '%cache_pool%'
               var_dir: var/site
               languages: [eng-GB]
               content:
                   default_ttl: '%httpcache_default_ttl%'
               http_cache:
                   purge_servers: ['%purge_server%']
                   fastly:
                       service_id: '%fastly_service_id%'
                       key: '%fastly_key%'
   
           admin:
               page_builder:
                   siteaccess_list: [site]
   
           mybo:
               page_builder:
                   siteaccess_list: [fr]
   

3. Try to edit any content

Result
You will see that every form fields are unstyled and there is no AlloyEditor in the RichText fields. See also attached screenshot.

Note
The customer reported, that if he manually add:

            admin_ui_forms:
                content_edit_form_templates:
                    - { template: '@ezdesign/content/form_fields.html.twig', priority: 0 }

to the one of admin siteaccesses, then content edit view is rendered correctly.