Almost every FOSS software I have installed shows what’s changing with the next version before you click the upgrade option. Audacity gives you a link to read more about the updates.
My suggestion is to add a clickable link to the version notes you publish on the News section of the webiste, and/or a link to Github on the About Shoutcut’s window. This would eliminate one click or many clicks to find the GitHub page.
Or have both links available in the Help section of Shotcut, and on the installer (if possible).
This is actually what a click on the upgrade notice does: take you to the release notes page first.
Showing them in a window inside the application instead of opening a browser tab is not much different and will not actually help people to read them. I feel like you are just asking for a change because it is different than other applications when actually every one is different.
Why? It is not necessary to go to a GitHub page. Honestly, if one cannot use one of the existing web site links already in the Help menu and navigate the web site…
There are a lot of questions on this forum that would never need to be asked if people would read the release notes before asking the question. But I do not know if adding the release notes into the interface would cause more people to read them.