We can try:

    $cmsBlock = $this->blockInterfaceFactory->create();
    
    $copyrightBlock = $cmsBlock->load('copy-right','identifier');
    //And then check
    
    if (!$copyrightBlock->getId()) {
     ......
    }

Take a look: `vendor/magento/module-cms/Setup/InstallData.php`
    
    $footerLinksBlock = $this->createPage()->load('footer_links', 'identifier');

**[EDIT]**

Seem that `load` method will be deprecated in the future.