Learn GTK Glade Programming
With Linux phones becoming a reality, it would be nice if there were more useful apps developed for them.
The Mobile OS known as "Phosh" uses GTK for it's apps, as does the Gnome desktop environment and the Gnome derivatives (Cinnamon, Mate...etc.).
Glade is an application that makes it much easier to lay out the GUI interface for your GTK app, which you can then tie together with code in whichever IDE you like best, such as Code::Blocks, Anjuta, Eclipse, or VS Codium.
In the link below, Kevin O'Kane from the University of Iowa offers a series of 50+ videos on how to create GTK Linux programs in C using the Glade Rapid Application Development (RAD) program. You will need to know the C programming language. Udemy.com has a C Programming for Beginners course for $20.
https://www.cs.uni.edu/~okane/youtube.html#gui
And here is the link to the code used in the video tutorials.
https://www.cs.uni.edu/~okane/Code/Glade%20Cookbook/
This is the 1st video in the series:
https://www.youtube.com/watch?v=g-KDOH_uqPk