Applications available out-of-the-box do not use the correct Spanish locale variant

When you set up a new installation of Windows 10, version 1809 or a later version, you select one of three Spanish locale variants: Catalan (ca-ES), Basque (eu-ES), or Galician (gl-ES).

After you finish Windows Setup, you open the Windows Store, and you see that the application listings appear in English.

Additionally, some parts of the Windows interface use standard Spanish (es-ES) instead of the locale variant that you selected.

This issue resolves itself after your computer connects to the internet. After the connection is established, Windows Update downloads and installs updates that include the appropriate locale resources.

If you cannot install Windows updates, you can change your language settings to Spanish (es-ES). To change any of your language settings, select Start > Settings > Time & Language.

This is a knows issue in Windows 10, version 1809 and later versions. 

This issue will be fixed in a future release of Windows 10.