Steps to reproduce:

1. Clean installation of Ibexa DXP v3.3.34.
2. Use the following configuration:

       siteaccess:
           list: [site, site2, test]
           groups:
               site_group: [site, site2, test]
   
   ezplatform:
       siteaccess:
           list: [admintest, admintwo, admin]
           groups:
               admin_group: [admintest, admintwo, admin]
       system:
           admintest:
               page_builder:
                   siteaccess_list: [ test ]
           admintwo:
               page_builder:
                   siteaccess_list: [ site2 ]
           admin:
               page_builder:
                   siteaccess_list: [ site ]
   

3. In vendor/ezsystems/ezplatform-page-builder/src/lib/Siteaccess/SiteaccessService.php in the resolveSiteAccessForLocation method, add the following lines under $availableSiteAccesses definition:

           $prioritizedSiteAccess = 'test';
           $availableSiteAccesses = ['site'];
   

4. The final resolved Site Access should be site, because it's defined in $availableSiteAccesses variable.
   This override will replicate an edge-case scenario.
5. Edit the default Landing Page.
6. Observe the log, one should find the following entry:

   app.WARNING: Cannot resolve siteaccess for language: eng-GB. Fallback to test [] []

7. Dump the final Site Access in the resolveSiteAccessBasedOnLanguage method.

Expected result:
test Site Access is resolved (outside of admin Site Access) scope.

Result:
site Site Access should be resolved.