Lawyers deal with confidential client information and we have a duty to secure that information. But it doesn’t matter who you are or how you use your technology. No one would want to donate, sell or give away a computer or phone without making certain your personal information is wiped. There is just too much information, like remembered passwords and saved text messages.
In the old days, I could confidently send lawyers off to Darik’s Boot and Nuke at https://dban.org/ after warning them to be cautious with whatever media they installed the tool on, lest they accidentally nuke something they didn’t intend to destroy. DBAN doesn’t work on SSD drives and they now sell a commercial product. Today we also have data on phone and other devices.
Today the respected tech website Wirecutter published an excellent guide How to Securely Wipe Your Computer, Phone, or Tablet. You may want to bookmark this guide so you will have it handy when you need it.
So, what about a dead computer? The quickest solution is to do an internet search to find instructions how to remove the hard drive from your model of computer and remove it before recycling or discarding the computer. Then you can physically destroy the hard drive. My son and I used lighter fluid to barbecue some old hard drives once and you can also let them soak in some caustic liquid for an extended period.