I noted elsewhere that a bug in Joomla's update routine is throwing false positives regarding extensions needing an upgrade prior to migration. Just today, I've started to see Admin Tools appearing as extensions requiring upgrade prior to migrating to Joomla 4.
I decided to take this with a grain of salt, and it was the only extension Joomla was complaining about (apart from a few other random ones in the "We couldn't tell" section which I had the latest, and J!4 compatible, installs of). So I went ahead and did the Joomla upgrade. The upgrade for Joomla was fine, but I DID have an Admin Tools issue:
An error has occurred.0 Call to undefined method Joomla\CMS\Application\AdministratorApplication::isAdmin()
As I can't upgrade to a Joomla 4 version prior to migration, do I need to uninstall Admin Tools, migrate then install the Joomla 4 version.
Apologies if this has already been asked and answered. I did have a look but couldn't find any posts.