Have you ever wished that you could freeze your Linux desktop screen and draw anything on it? Or, you may want to point out or highlight a part of your app or desktop to someone else while screen recording on Linux?
If so, Gromit-MPX is an easy-to-use on-screen annotation tool that you could use right now.
Under X11, it enables graphical annotations with several pointers at once or a dedicated annotation device setup where you can use a second pair of input devices to annotate while simultaneously continuing to work normally with the first pair.
It was an easy AUR install for me on Manjaro and works well. Gromit-MPX is pressure sensitive, if you are using properly configured XInput-Devices you can draw lines with varying width. It is possible to erase something with the other end of the (Wacom) pen.
See Gromit-MPX Lets You Draw Anywhere On Linux Desktop Screen
Gromit-MPX is a free and open-source tool that lets you annotate anywhere on the screen. It supports all Unix desktop environments such as GNOME, KDE, and Xfce.