You could try to replace these lines in /opt/librenms/config/database.php
'charset' => 'utf8mb4',
'collation' => 'utf8mb4_unicode_ci',
with
'charset' => 'utf8',
'collation' => 'utf8_unicode_ci ',
That being said, mine is default with utf8mb4 so i’m not sure whats different between our setups.
Might be worth a try?