However, when I implemented my version, I realized that the header message was not being displayed on the HUB unless CTRL + F5 was pressed (a normal behavior for web). Then, how do you communicate with your users if they didn't receive the message?
In the document attached, I shared step by step how to implement a header message (my version) on the Qlik Sense HUB and what needs to be changed in order to force the client-side to be updated. Before doing any changes, ALWAYS make a backup of the files.
Here is how it looks like.
Although I didn't have implemented @berndjaegle 's suggestion, he explains how to add an URL to the header message in the original post.
Qlik Sense environment
Qlik Sense Enterprise June 2019 Patch 1.
Qlik Sense Repository Database is located in the central node server.
IMPORTANT: Keep in mind that the changes shared here are not supported by Qlik.