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I cannot reproduce this, when clicking "Undelete" it says that the file has been successfully undeleted

Not that button, the "change visibility" button. It only shows up if your user account has the correct rights, which admins might not have by default.

Try setting in LocalSettings.php

$wgGroupPermissions['user']['deleterevision'] = true; $wgGroupPermissions['user']['deletelogentry'] = true;

In T379070#10294956, @Bawolff wrote:

Not that button, the "change visibility" button. It only shows up if your user account has the correct rights, which admins might not have by default.

Try setting in LocalSettings.php

$wgGroupPermissions['user']['deleterevision'] = true; $wgGroupPermissions['user']['deletelogentry'] = true;

Oh right, my bad. I tried it again and clicked on the correct link and it leads me to index.php?title=Special:RevisionDelete&type=filearchive&target=File%3ATestFile.png&ids=4 which appears to be the correct URL, according to the task description.

I mean the circled button "change visibility of selected revisions", not the text link.

To me, it looks like the "Change visibility of selected revisions" button belongs to the "Page history" section and only applies to those revisions. You get the error because you did not select any page history revisions.
For the File history section, you can use the "change visibility" links which work fine for me. I might be wrong though, it would probably be good to have someone review this who has more knowledge about this page.

Right. The point of this bug is it is confusing to have the checkboxes beside the items in the file history section if they do not do anything. They should either be removed or connected to the button.