By now it is on Commons no longer possible to add site links through the
{F34496408 size=full}
as shown here as soon as you fill in the field for the language the next field page is not accessible.
this is really annoying as you need to manually create the item in wikidata in order to add the interwikilinks.
Steps to reproduce:
1. Go to a Commons category that does not yet have a Wikidata item associated with it - example https://commons.wikimedia.org/wiki/Category:Coaches_of_Everton_L.F.C.
2. Click on 'Add links' a the bottom of the sidebar
3. Enter 'en'
4. Normally this would present a list of options, and you could select 'enwiki' - but it no longer does this.
5. Normally you could then enter a page name, but this option remains greyed out, and you can't click the 'link with page' option.