Flameshot
Also on WindowsTakes screenshots and lets you draw arrows, boxes and text on them.
Installs from Ubuntu's own software archive.
Looking for Greenshot on Linux? Flameshot does the same job for free, and TuxPick installs it for you.
Install Flameshot with TuxPickIt works on Ubuntu 22.04 and 24.04, and on systems built on them like Zorin OS and Pop!_OS.