Linux

Dejavu, Liberation, & Noto are all pretty common.

I'm a sucker for jetbrains Mono when I need a monospaced font. It just looks nice to me.

Ubuntu uses their own font family. I think it’s one of the only distributions with its own custom font, but I might be wrong. The Unicode coverage of the Ubuntu font is not very big compared to Google’s Noto font family, which many distributions switched to as default. But it mostly depends on the DE — Gnome uses the Cantarell font, KDE uses the aforementioned Noto font.

I LOVE FIRA CODE (NERD PATCHED)!!!!

I usually install noto-fonts

Can't speak to how common they are, but I do like the Nerd Fonts, and particularly MesloLGS NF 10pt for my monospaced font. Very handy for Zsh Powerline10k and neovim.

Inter for GUI, Iosevka for terminal. Dejavu is my fallback option for some systems.

I like fira code w/ nerd fonts. The ligatures are nice for coding.

I use open dyslexia as I have dyslexia. Its very nice!

Hack Nerd Font Mono and Noto Sans for me.

I enjoy Fira Sans and Fira Mono. Looks professional without being extraordinarily boring.

I'm a fan of the Go fonts for terminals.

Usually I just use whatever fonts are default on the DE I happen to be using at the time, right now that'd be GNOME so I believe its Cantarell? I don't generally customize my normal (non-monospace) fonts because I can never find one that looks good everywhere. I like Google's "Product Sans" font for example, but it is definitely not one you want to use everywhere. Yet oddly enough on my Pixel, I believe Product Sans is the default unless an app explicitly changes it, and it looks good everywhere there. Or maybe I've just never given changing the default enough time to adjust to it, who knows.

The monospace font that I use is Comic Code, it sounds silly I know (I was skeptical at first too) - but it looks really nice in both my terminal and IntelliJ. Something about the font renderer that is used by default (I can't think of the name for some reason, FreeType maybe?) makes it look really nice and sharp. On Windows, it looks too thin, and on macOS it looks too thick - Linux is truly the "golidlocks" for this font it seems.

But, the Intel One Mono font looks nice too.

I have settled on mplus code, I really like its condensed look.

https://www.programmingfonts.org/#mplus

I don't think it's that common, but if you're looking for good fonts, I really like IBM Plex Sans/Serif/Mono. Has good Unicode coverage as well and is "open source" (or whatever it's called for fonts).

I've been using JetBrains Mono Nerd Font for my terminal as of late and Inter for my GUI's.

Ubuntu fonts works pretty good for me as a general UI font tbh. In text editors I prefer mononoki over monospace, it's a bit prettier IMO, although in terminal I use terminus because pixel fonts are cool.

I use noto fonts for web browsing and general GUI stuff and I use Cascadia Code in the terminal

it's Jetbrains where it's at..

I generally install MS Office Fonts, some Adobe Fonts and then Fira Code Nerd Font too.

Lots of great fonts and families mentioned so far in this thread, but no-one has mentioned my current and long-time favourite for almost all environments and applications: Input.

$ echo sans serif monospace | xargs -n 1 fc-match
InputSansCondensed-Regular.ttf: "Input Sans Condensed" "Regular"
InputSerifCondensed-Regular.ttf: "Input Serif Condensed" "Regular"
InputMono-Regular.ttf: "Input Mono" "Regular"

I have a weird selection- Jetbrains Mono with Monocraft and the bold Minecraft font. Jetbrains Mono is for everything except discord. Monocraft with Minecraft Bold is for Discord which i have IRCified with a custom Vencord theme.

I use fantasque for my monospace, fira sans for my work horse ui font, and Garamond for my "someone wants to display serifs for some reason"

Not common, perhaps, but I like to download Atkinson Hyperlegible.

Iosevka

Ubuntu / Ubuntu Mono are my favorites.

I use Fedora, but I still install Ubuntu font because I prefer it lol

I use the entire Apple's SF suite (including New York)

Lexend fonts, they increase reading speed, offer more precise size control, and have the extra perk of being more accessible for differently abled readers. I like to familiarize myself with "accessible" design, the more we get used to it as normal the better our world can get.

My preference for a few years have been a combination if IBM Plex Sans for most stuff and Iosevka for monospace. They both look amazing! Iosevka might look a bit weird when first seeing it but I can't really use anything else these days. However, Fira Code is a really good monospace font as well.

I like Iosevka for programming and terminal.

MathJax Sans Serif

Google Sans Text, Cabin, Fira Sans, Roboto, Noto

For monospaced Jetbrains Mono, Fira Code, Iosevka

For sans and serif font, Noto Sans and Noto Serif.

I really like CaskaydiaCo[d|v]e.