I want to provide a quick update for this topic. this feature will be in progress soon, show timestamp on attachments, and it is being under consideration to be prioritised in the next couple of months. we will keep you posted with the updates. I know this has taken a while to build out, but rebuilding Jira issues is no small feat, so we very much appreciate your patience on this.
In the meantime, you can opt out of this new issue experience via your Personal Settings > Jira Labs section will have a 'new issue view' toggle to turn it on or off. We will not be disabling this opt-out option until we have rebuilt all the key features of the Jira issues experience you have come to know and love.