I’ve been very happy with SijmpleScreenRecorder but I must say VokoscreenNG looks very good and seems to cover everything with a nice new interface. I was missing shortcut keys for pausing recordings but found them in the help screen (not sure if you can customise them). Another nice touch is the magnification function you can enable.
I love the visual way it does the rectangular area selection. Only quirk is you can’t move it between screens (but move the app to the correct screen and then select area, seems to do the trick).
Although AUR shows this in the repo’s as "vokoscreen" it is in fact VokoscreenNG as is seen by version number and when it starts up.
See Meet VokoscreenNG: An Open Source Screencast Tool
vokoscreenNG is a free and open source screencast software. It is created from scratch using Qt and GStreamer. Check out how to install it on Ubuntu and other Linux.