folkhack

OS: Debian 10 + XFCE

Terminal: highly-customized Terminator bound to F1 + XFCE Terminal for "floating" instances

Text/Programming: Sublime Text, Intelij IDE, nano (yeah yeah bring your hate vim users - I know it well and I'm not a fan), Meld

Markdown/docs: Typora (TRY THIS OUT IT'S AMAZING.)

Browsing: Chrome, Chromium, FF, Brave (in that order); Postman for API work, Charles Proxy for reverse-engineering work

Communication: Hangups (CLI), Discord

Containers/Virtualization: Docker, VMWare Workstation (I run a full Win10 LTSB underneath with all quick-access to my Adobe Creative Suite, saves time not having to switch to the MBP)

Transfer: Qbittorrent, Filezilla

Misc: Remmina for RDP, Kazam for screen recording, pgAdmin4 for working with my Postgres DBs, ncspot (CLI) for Spotify client; KeePass2 for password management in a file-based DB; GParted for partitioning

Ninja edit: Sublime Merge looks amazing... I will be trying this out ASAP.

SanderSantema
As an open-source alternative to typora I can suggest Marktext https://github.com/marktext/marktext which I believe is on par with typora features. Don't be alarmed by the fact that it's electron, it's pretty fast either way. And as far as I know typora is electron based too.