Question

How do I need to specify a language override for my template in order for Joomla! to use it?

It’s specific language tags for the COM_STORELOCATOR component.

<languages folder="language">
    <language tag="en-GB">en-GB/en-GB.tpl_XXX.ini</language>
</languages>

Answer 1

Option 1

The file with overrides should be located here:

/language/overrides/en-GB.override.ini

You can manage the template overrides directly from the Joomla! backend.

Go to Extensions > Language Manager > Overrides

Option 2

Check the solution proposed by “mgirardis” in the Joomla! Forums:

You create the folder: [TEMPLATE_NAME]/language/overrides

and put inside it the file containing all the desired overrides:
zz-ZZ.override.ini where zz-ZZ is the language you wish to override.

Then in templateDetails.xml you add (inside the tags <languages>; I’m
putting this tag here only to illustrate the idea):

<languages>
    <language tag="overrides">language/overrides/zz-ZZ.override.ini</language>
</languages>