I've just come across a very interesting series about making a GUI application with SDL. https://youtube.com/watch?v=6hIaEHzlmFc. Despite the fact that #SDL2 is used, the code can be easily ported to #SDL3. Thank you @icculus!
Writing a simple media player with SDL, part 1.

YouTube
@laladrik I haven’t finished the project yet! But there is a lot of content there to get you started!
@icculus It sounds exciting. Are you planning to migrate the project from SDL2 to SDL3?
@laladrik yeah, that should be the next video!