Try

Author: VincentLanglet

src/Doctrine/Orm/Filter/PartialSearchFilter.php

@@ -44,9 +44,9 @@ public function apply(QueryBuilder $queryBuilder, QueryNameGeneratorInterface $q
 
         if (!is_iterable($values)) {
             $parameterName = $queryNameGenerator->generateParameterName($property);
-            $queryBuilder->setParameter($parameterName, $this->formatLikeValue(mb_strtolower($values)));
+            $queryBuilder->setParameter($parameterName, $this->formatLikeValue($values));
 
-            $likeExpression = 'LOWER('.$field.') LIKE :'.$parameterName.' ESCAPE \'\\\'';
+            $likeExpression = 'LOWER('.$field.') LIKE LOWER(:'.$parameterName.') ESCAPE \'\\\'';
             $queryBuilder->{$context['whereClause'] ?? 'andWhere'}($likeExpression);
 
             return;
@@ -55,8 +55,8 @@ public function apply(QueryBuilder $queryBuilder, QueryNameGeneratorInterface $q
         $likeExpressions = [];
         foreach ($values as $val) {
             $parameterName = $queryNameGenerator->generateParameterName($property);
-            $likeExpressions[] = 'LOWER('.$field.') LIKE :'.$parameterName.' ESCAPE \'\\\'';
-            $queryBuilder->setParameter($parameterName, $this->formatLikeValue(mb_strtolower($val)));
+            $likeExpressions[] = 'LOWER('.$field.') LIKE LOWER(:'.$parameterName.') ESCAPE \'\\\'';
+            $queryBuilder->setParameter($parameterName, $this->formatLikeValue($val));
         }
 
         $queryBuilder->{$context['whereClause'] ?? 'andWhere'}(