Are you sure latest CB Redirect Bot is installed? It's quite literally impossible for this to be happening. It's directly version checking against Joomla's major version constant. CB Redirect Bot is installed on our demo site and our test environments working fine on Joomla 3, 4, and 5. The only thing I can think of is the wrong version is installed or your migration extension poorly migrated Joomla and you've mixed Joomla files (e.g. the version constant is broken) that shouldn't exist anymore.

My recommended steps for migration are as follows.

1. Update to latest Joomla 3
2. Update all extensions and plugins for those extensions
3. Unpublish all extensions that are not marked Joomla 4 compatible
4. Switch to default Joomla 3 template (your j3 template is unlikely to be j4 compatible)
5. Update to Joomla 4
6. Update all extensions needing Joomla 4 version
7. Publish previously unpublished extensions after updating to their Joomla 4 versions
8. Redo template as you'll likely need a new one for Joomla 4

You should not need a migration extension at all. It's a pretty straight forward update process. This is the only process we test. I cannot account for what migration extensions maybe doing.