The API call link in the example in https://www.mediawiki.org/w/api.php?action=help&modules=flow%2Bview-topiclist (which is embedded on https://www.mediawiki.org/wiki/Extension:StructuredDiscussions/API#view-topiclist ) is broken.
It gives an "invalid-page" error.
That is because the page https://www.mediawiki.org/wiki/Talk:Sandbox has been redirected to https://www.mediawiki.org/wiki/Talk:Sandbox/Structured_Discussions_test in the meantime.

The call to https://www.mediawiki.org/w/api.php?action=flow&submodule=view-topiclist&page=Talk:Sandbox needs to be replaced by calling https://www.mediawiki.org/w/api.php?action=flow&submodule=view-topiclist&page=Project%20talk:Sandbox/Structured_Discussions_test instead.

The line 'action=flow&submodule=view-topiclist&page=Talk:Sandbox' in the file includes/Api/ApiFlowViewTopicList.php in the code repository mediawiki/extensions/Flow needs to be updated.

Tempted to mark this as good first task but I have no idea what that means for Flow installation which are not located on the server mediawiki.org.