Ask HN: Best electronic devices to fix for education and profit?

I just had a great afternoon fixing my old laptop, and it works really well now. I'm a web dev, and had never fixed hardware before, but it was so much fun, and I've probably added ~£200 in value from only ~£50 in parts.

I now want to have a go buying a faulty device and fixing it up (mainly to learn, and hopefully make a bit of money by flipping it). Are there any good devices or genres of devices good for this? E.g. I've seen videos of people buying 10 faulty Nintendo Switches, fixing them up and reselling. Thanks.