For some reason that is completely unknown to me, only two or three wall sockets in our rental apartment are actually grounded — in the kitchen and laundry room.
All the other ones actually have grounding wires present, they're just not used, and often tucked away into the wall without so much as electrician's tape covering it. How this passed inspection is beyond me. As I prefer my devices to be grounded whenever possible, I have been slowly going through the apartment replacing a wall socket at a time. This is just a rental we're in, but for our own comfort and, well, safety, I figure it's a worthwhile cause.
Safety warning: Please don't take what I'm about to show you as a guide on how to do this yourself. Working with electricity is dangerous and can get you killed. If you don't know what you're doing, or are not 100% confident in your own skill-set, please let a professional do it for you. That's what they're there for.
While moving my homelab to it's final-for-now location, it was time to upgrade this socket that we have behind a book case in that room. I first kill electricity to this part of the house using my usual method (plug in a lamp, turn off sections until the light goes out), and confirm there really is no electricity by using a multi-meter.
As per "usual" in this place, whomever installed these wall sockets had no regard for following proper color coding or safety for that matter, with two ground wires twisted together as shown above, without any protection around it. It was just jammed in there. It's amazing this hasn't caused issues so far, to be honest.
Before I can install the new wall socket, I have to make sure these wires in here are actually grounding wires. The best way to do that, unfortunately, involves turning the power back on with the wires exposed/accessible. I could then —carefully— use the multi-meter to see if the wire is in fact ground. To measure this, you measure between the "live" and ground wires.
And that's all there is to it. To be honest the only challenging bit of doing these kinds of small fixes around the house is when they're not following code or color conventions (which, especially if you're not careful, can be incredibly dangerous) and, well, you working with dangerous levels of electricity.