- Obsidian - great markdown-based note app
- NewsFlash - fast and elegant RSS news reader
- Bottles - program to run Windows apps and managing them easily
- BreakTimer - a life-saver for me; it allows you to set a break after given amount of time
- LibreWolf - privacy-focused fork of Firefox
There are a lot of awesome programs on Linux, I recommend browsing Flathub to find them
And like many people mentioned here, TLE, Veronica Explains and Tilvids are also worth recommending.