Create a new branch 4.0.x so we can drop D9 support, raise the minimum core version to Drupal 10.3 and start adding Drupal 11 support.
8.x-3.x will continue to work for Drupal 9 and Drupal 10.2. There are many breaking changes in Drupal core that make it difficult to support D9, D10.2 and D10.3 in the same codebase without a lot of conditional code. That is why I've decided to put all the changes into the new branch and leave the old branch for "legacy" sites.
Fixed
4.0
Code