There are some projects I have to move from my old desktop, and I've got a few in the works, so expect to see them here soon.
Tech That You Should Use
Using a password manager is an essential security measure. It's a program that uses a master password to decrypt an encrypted database of computer-generated passwords, which you copy and paste into online login forms. Why is that important? If you have multiple online accounts, as all modern people who aren't hermits do, you must use different, secure passwords for each account. If you re-use the same password for every account, one of them will be compromised, and when it is, all of your other accounts will be too. Not so bad for your bin weevils account, but think about your online banking, social media, instant messaging, etc. The alternative of remembering multiple different secure passwords is infeasible, unless you're a sauvant. Using a password manager is thus more secure and more convenient. I use KeePassXC. It's better to use an offline password manager, since the databases used by online services are targets for attack and may (read: will) be compromised eventually. But this can be inconvenient if you want to access your accounts from multiple devices. A potential solution is to use rsync to sync your passwords file between computers.
A firewall is an essential security measure that monitors network traffic to prevent malarkey and shenangians. I use nftables. See the arch wiki page on nftables for how to install, use, and configure it. Other operating systems will have their own alternatives.
It's good for the eyes, especially late at night. For dark mode I use the dark reader browser extension, which is available on chrome- and firefox-based browsers. I don't know if there's an equivalent for pale moon. For blue light filtering I use the colour correction settings in nvidia-settings. There's an in-built blue light filter in Windows 10, and I'm sure there are all sorts of solutions on other operating systems.
A mechanical keyboard
They're so much better than rubber-dome keyboards, the only way to really appreciate it is to go ahead and get one. They're nicer to type on, more durable, easier to clean, - the benefits are endless. Literally the only reason they're not the norm is that they're more expensive. I use a corsair K95. While you're at it, make sure you have correct posture when you're using a computer: the monitor should be positioned so you look straight forward at it, not down, and sit up straight with the keyboard positioned such that your elbows are at a 90 degree angle while you're typing.
Note: these solutions probably don't work for smartphones, or may require workarounds, but I don't know what they are and have no interest in finding out. The fundamental problem is that smartphones are designed to minimise the control that the user has over what is supposed to be his own device. My recommendation is to get rid of your smarthphone and get a dumbphone instead. I haven't owned a smartphone for ~2 years, and out of any single decision I've made, getting rid of the thing is the one which has improved my life the most.
For tech nerds
These ones probably won't appeal to non-techies, and aren't so much essential, but will improve your experience with your computer immensely. They also require some set-up and getting used to, and may inconvenience non-techy users.
There are some cases where a graphical program is better, like a web browser or an image manipulation program, and I can understand if you're not a tech nerd, but why tech-literate people use graphical file managers and text editors is beyond me. Terminal-based programs run faster, are faster and easier to use, tend to be more powerful/extensible/all the other unix buzzwords, require less processing power and memory, and can be run outside of a graphical environment, which is useful for troubleshooting if your graphical environment breaks (this has happened to me and will happen to you if you want to do any customisation). As a rule I use terminal-based programs whenever it's a viable option. Some of the terminal-based programs I use:
File manager: ranger
Text editor: nvim
BitTorrent client: transmission
Audio control: pulsemixer
RSS reader: newsboat
A tiling window manager and keyboard-based workflow
Tiling window managers are to desktop environments as mechanical keyboards are to rubber-dome ones. Once you use one, you'll wonder why they aren't the norm. I switched to awesomewm ~6 months ago, and it was only when I used the university's linux virtual machine that I realised how slow and clunky having to drag the mouse and move all the windows around is. I use awesomewm because it's the most popular one that's licensed under the GPL.
RSS is a simple, consistent, direct, advertising- and tracker-free way to get a news feed/updates from people on the 'net. Opening a browser, going to your bookmarks, clicking through all of the junk, ads, and general soy-ware is annoying, but with RSS it doesn't have to be that way. See Luke Smith's videos on RSS.
A good web browser
Chrome and firefox are cringe. Of the many far better alternatives, Brave is the best.
Browser extensions for malarkey prevention
I use the following:
uBlock Origin - blocks ads
uMatrix - the single best browser extension, allows you ultimate control over where your browser is allowed to connect, what type of data it is allowed to download, and what it is allowed to execute
ClearURLs - removes tracking elements from URLs
ForgetMeNot - makes the browser forget website data (cookies etc.)
SmartHTTPS - always use HTTPS where the site's server supports it
User-Agent Switcher and Manager - the name is self-explanatory