After digging through many bug reports I found a solution to the issue I was facing. The problem I was having is related to a new feature in 6.0 for sites with over 10K user accounts which automatically disables the author dropdown in Bulk/Quick edit. I’m not sure how they decided that was a good idea but se la vie. Here is the solution they offered which I tested and it works as expected.

Add the following code snippet to your theme or in my case a muplugin:

add_filter( 'wp_is_large_user_count', '__return_false' );

And as they say in Dublin, “Bob’s your uncle!”