In L-4 it was simple:
$random_quote = Quotation::all()->random(1);
But now in L-5 not a single method described in this post is working: Lar
orderByRaw('RAND()')
Note: It will take in ram all the rows from the rest of the query, so if you have a large table whithout other filters in the same query it will give bad performances, otherwise this is your option