Can't remember if it's a default keybinding or if I changed it, but I use shift+meta+s to select a rectangle of the screen to copy. In KDE I have to select "copy" from the notification hamburger menu, Xfce I configured to automatically copy it to the clipboard. Then you can upload the selection to Discord and other apps with ctrl+v. Just meta+s copies the entire screen but I use that much less often.
Can't remember if it's a default keybinding or if I changed it, but I use shift+meta+s to select a rectangle of the screen to copy. In KDE I have to select "copy" from the notification hamburger menu, Xfce I configured to automatically copy it to the clipboard. Then you can upload the selection to Discord and other apps with ctrl+v. Just meta+s copies the entire screen but I use that much less often.
Try Flameshot for screenshots! I bound it to my printscreen key.