My smooth brain can't unlearn pressing back to close an image that I've opened.
Is it functionally possible for the back behaviour to have a toggle to change it from going to previous page to instead close the image in first instance? Enjoying wef wef so far after coming from rif!
I made a thread on this issue before and it had a positive reception and someone opened an issue in the tracker since. It may just be slightly under priority, considering the updates since then all had important features, so let's be patient.
It is possible in modern browsers. You can add a url hash when opening the image viewer and add a listener to the window.onhashchange event to close the viewer. I believe there's a jQuery polyfill as well.