It is possible to have the query pick a random entry.
From the Craft Entries Fields docs we see that entry.entriesFieldHandle
is a shortcut for
craft.entries({
relatedTo: { sourceElement: entry, field: "entriesFieldHandle" },
order: "sortOrder",
limit: null
})
And what we want is to order the entries randomly, and then limit the number we retrieve to only one:
craft.entries({
relatedTo: { sourceElement: entry, field: "entriesFieldHandle" },
order: "RAND()",
limit: 1
})
So to retrieve one random entry and get its url:
{% set randomEntry = craft.entries({
relatedTo: { sourceElement: entry, field: "entriesFieldHandle" },
order: "RAND()",
limit: 1
}).first()
%}
{% if randomEntry %}
{% set randomUrl = randomEntry.url %}
{% endif %}