In #3068722: Don't allow block restrictions for individual content blocks → (added 4 years ago), this module made the decision not to restrict Layout Builder Styles for individual block instances.
In Drupal 10.1, per https://www.drupal.org/node/3320855 → , the internal name for these types of blocks changed from "Custom" to "Content." This resulted in the existing code to cease working:
// Remove individual reusable blocks from list.
unset($blockDefinitions['Custom']);
1. Create a content block.
2. Configure a Layout Builder Style.
3. Under the "Block restrictions" section, there should not be a section titled "Content blocks" but there is.
Restore the previous skipping of restricting Layout Builder Styles to apply only to specific content blocks by updating references from "Custom" to "Content."
2.0
Code
Changes look good to me, unless we want to drop support for 10.0, similar changes I have done here: #3431601