Flameshot has gotta be the best screenshot tool on Linux -- annotations, colors, and destination upload. It only has an Imgur upload destination though. - Source: Reddit / about 1 month ago
This may be too specialized for your interests, but I'd love to see a more fully-featured image editor/annotator for Flameshot. It's a screenshot tool that allows you to add text/blurring/arrows, etc. But it lacks some features that I like from Windows-only tools like snagit:. - Source: Reddit / 29 days ago
shotgun (screenshot utility) - Minimal X screenshot utility written in Rust
ShareX - ShareX is a free and open source program that lets you capture or record any area of your screen...
Greenshot - Greenshot is a free and open source screenshot tool that allows annotation and highlighting using the built-in image editor.
Gnome Screenshot - GNOME Screenshot is a utility used in the GNOME desktop environment for taking screenshots.
LightShot - The fastest way to take a customizable screenshot.
Snipping Tool - Use Snipping Tool to capture a screen shot, or snip, of any object on your screen, and then annotate, save, or share the image