They don't test their plugin with the best/higest selling premium themes, so they have zero clue if their plugin with work with those themes or not. They just blindly hope that their plugin works and if it doesn't, it's the Theme's fault only.
I am mostly writing this review to counter what was written here:
crudoadmin — March 5, 2021 — Its a piece of junk
In my experience, the URL, Description and Avatar boxes are only greyed out if you haven't yet added an Author Name. If that first field (Name) is empty, then the other fields are disabled. This is to prevent people adding data to those other fields without providing an author name. Makes perfect sense to me. I suspect "crudoadmin" might not have taken the time to really test out what was going on.
As for the plug-in itself ... works well. Out theme was even able to pull in the image, URL, and description (in the same way it pulls in the image, URL, and Bio from a registered user/author). Which means this plug-in is storing that info in standard Wordpress fields, as opposed to making something up (which was the case with the Simply Guest Author plug-in, which we had to ditch for that very reason).
It only allows to change Author to Guest and ad a name to the author, but it does not allow to add an Avatar (it's greyed out) nor a url (it's also greyed out) and in the post the "guest Author" name is not shown correctly but instead it shows the website's admin user.
In my case I needed something that would create the admin part an I can then use it on my custom theme. Definitely saved me some time to create my own custom meta boxes for the posts. Needed only to customize the single post template page to show the guest meta information.