SQL-DATABASE ERROR

Database error in WoltLab Burning Board (2.3.6): Invalid SQL: SELECT COUNT(articleid) FROM bb1_lexika WHERE visible = 1 AND catid = 6 AND INSTR('ÄäÖöÜü',UCASE(LEFT(topic,1)))>0
mysql error: Illegal mix of collations (utf8mb4_general_ci,COERCIBLE) and (latin1_swedish_ci,IMPLICIT) for operation 'locate'
mysql error number: 1267
mysql version: 10.11.6-MariaDB-0+deb12u1
php version: 7.4.33
Date: 23.04.2024 @ 07:32
Script: /radioforum/lex.php?action=letterlist&catid=6&letter=%C4%D6%DC
Referer: