What's something that's not common knowledge but you think everyone should know?

Health related:

• "Healthy food" is a grift meant to sell you shit. And by that I mean most "Healthy Foods" you find on the supermarket or are advertised as superfoods or are at the core of the latest fad diet are in fact just as trashy as any other ultraprocessed prepackaged food. Even if they are truly healthy foodstuffs, they are often something that isn't a staple of people's everyday diets (usually shit that is part of the diet in a foreign culture, but not on the West) that you get massively overcharged for because "Muh superfood".
• The real way to eat healthy is to buy fresh ingredients, cook your own meals, and inform yourself on what your body actually needs so you can be smart about what you cook... But that requires time and work investment, which most people cannot afford to do, which is why obesity is more common in poor folk than on rich folk. Have I mentioned that knowing certain stuff will make you, if not politically radicalised, very angry regardless?

Computer related:

• In windows 10 and 11 if you press Win+V instead of Ctrl+V you'll get the option to activate clipboard history. After that, you can use Win+V to get a little menu that lists things that were in your clipboard and which you replaced by copying/cutting something else. You can then choose what to paste. Linux has plenty of programs that add this functionality and was in fact there first. No idea about MacOS.
• Learning a bit of your operating system's command line interface will save you a lot of time and effort in the long run -- And you don't need to become one of those turbo-weirdos that uses nothing BUT the CLI -- But the reason the good ol' console-host/terminal-emulator has stuck around after all these years is that there is a lot of shit that is just faster and more practical to do by typing a few words vs. going through 10 different menus and tabs.
• Save yourself some money: If you're not gonna be doing hardcore state-of-the-art gaming or heavy video editing or some other intense task, a middle-of-the-road computer from ten years ago with some light upgrades will carry you just fine. Get a used PC, get a decent quality SATA SSD and some extra sticks of RAM (8 minimum, ideally 16 or more) and you'll be all set for everyday internet browsing and office tasks and shit. Heck, slap in a GPU later and you can get away with playing a lot of games, if not with DigitalFoundry tier performance.