For wikidata, there exists a resolver at https://tools.wmflabs.org/wikidata-todo/resolver.php, which allows me to build URLs such as

https://tools.wmflabs.org/wikidata-todo/resolver.php?quick=VIAF:12307054 , or

https://tools.wmflabs.org/wikidata-todo/resolver.php?prop=P227&value=120434059

in order to address wikidata items directly from their external identifiers.

Squid is more appealing for viewing the items. Does a similar mechanism exist there?

Cheers, Joachim