After noticing the error I tested the Plugin with only ACF active and the Twenty Twenty-Four Theme. Still this is what I get on media-options.php:
Fatal error: Uncaught TypeError: Cannot access offset of type string on string in /home_pr7/b/l/xxxxxx.ch/htdocs/xyz/web/wp-content/plugins/acf-image-crop-add-on/acf-image-crop-v5.php:707 Stack trace: #0 /home_pr7/b/l/xxxxxx.ch/htdocs/xyz/web/wp-admin/includes/template.php(1836): acf_field_image_crop->displayHideFromMediaInput(Array) #1 /home_pr7/b/l/xxxxxx.ch/htdocs/xyz/web/wp-admin/includes/template.php(1790): do_settings_fields(‘media’, ‘acf_image_crop_…’) #2 /home_pr7/b/l/xxxxxx.ch/htdocs/massimos-palace/web/wp-admin/options-media.php(172): do_settings_sections(‘media’) #3 {main} thrown in /home_pr7/b/l/xxxxxx.ch/htdocs/xyz/web/wp-content/plugins/acf-image-crop-add-on/acf-image-crop-v5.php on line 707