Answer by Patrick Kenny for How do I automatically add a title to imported entities?

There is certainly a more elegant way to do this, but for now I decided to patch the validator itself in /feeds/src/Feeds/Processor/EntityProcessorBase.php:

if ($label || $label === '0' || $label === 0) {  $messages[] = $this->t('The @entity %label failed to validate with the following errors: @errors', $args);  if (mb_strtolower($this->entityTypeLabel()) === 'media') {    // Media will automatically have the title set to filename, so allow this.    return;  }}