Would you buy second hand phone / laptop?

No I always invest a little bit more and buy something as soon as it gets on the market and try to use it as long as possible. So I for example I am currently still using an Oneplus-5 that i now have for 3+ years and its specs are still higher then most Iphones or other phones around the same price now. I hope to use it for an other 3 years.

When I need something for a hobby project I most of the time get it for free from family or take the part from a broken item. The only exception is for games. In the past I bought nearly all gameboy games and ds games second hand from a local shop.

Absolutely yes, right now I'm running an old Dell Latitude which I bought from shops selling old corporate laptops. It's powerful and was under warranty before the purchase. It's no brainer buying second hand electronic items if you have the know how and know where to look. The new and fancy electronic items are often several magnitudes expensive and worst of all lose their value quickly. For phones I prefer buying month old phones from people who bought them but didn't like them for some reason. Again huge savings.

I always use second hand laptop, but only ThinkPad and stay away from used Dell's.

The reason is that you can get used ThinkPads , recent enough and at a significant discount but still covered by warranty, and Lenovo will honour such warranty.

Dell instead (Dell Italy, specifically) asked for the original purchase receipt to honour warranty still valid according to their website and plain refused to honour warranty without it.

Other brands, I don't know, but since I get a "new" laptop only once every three years at least, I wouldn't risk it.

Sure. My chromebooks were $69 on Woot. They clearly came from a school. My main machine is a 17” $600 Asus gaming laptop with 970M. It was $1500 new and runs like a dream. My iPad 4 was used. My iPhone 8 Plus was used.

I pay 50% or less for all used technology. I know when I see a good deal, which is not true for many people.

Yep. I have mostly purchased open box and 2nd hand computers in my life.

My latest computer was $400 off ($1600 usual price) just for having been opened.

Just make sure to wipe it/reinstall the software.