Gin admin theme dark mode by default

That's a very good idea.
I always do the same when I install Drupal because it's a lot less painful for the eyes when you're sitting in front of a 38-inch screen. I think that would be a very good default setting.

I wouldn't enforce dark mode on everyone. If anything, setting the auto mode which uses the user's system settings is more appropriate.

Maybe we can document somewhere how to enable it via crush, then? So anyone who like to do so can combine it with a drush si.

The drush command would be drush config:set gin.settings enable_darkmode auto, but I'm not sure if drush commands are relevant for the target audience of Drupal CMS. Configuring this through the UI would probably be the recommended way.

My motivation for raising was 100% based on the UX for the target audience of Drupal CMS.

If we're not keen on making "admin mode" more obvious, then perhaps we could add it as something a new user might want to consider after they've initially launched it. I know there's some "welcome" type pieces already delivered with Drupal CMS, so perhaps we could add to that content.

Interesting, I'm asking myself why it actually matters to recognize the difference between the admin and the frontend theme. Sure, it has lots of technical implications, but how is this important to the end-user?

I think when it comes to inexperienced users who want to try out Drupal and get to grips with the CMS, a clear visual dividing line between the frontend and the administration area is very helpful to know directly which part of the page you are currently on. This is exactly where this approach plays a role. That's why I can certainly understand the approach. However, I am also aware that not every user will prefer dark mode. But offering users the chance to try out dark mode as part of a guided tour, for example, could help here. I don't think it's the best solution to do this as a matter of principle.

Pointing out the difference between light mode and dark mode and letting the user decide what they would like is, I think, a better approach. Incidentally, you could also make the whole thing dependent on the user's system settings. There are already 1 or 2 issued in Gin for this.

Just playing devil's advocate: why is it helpful for a non-technical user to know about backend and frontend? Isn't it a huge benefit that they don't have to bother about that?

For me it makes the distinction between what I can see as an admin (or content editor or whatever admin-y role I have) and what the user will see much clearer. I appreciate there's outliers with the View / Edit / Delete... toolbar, but one of my original screenshots would be a good example.