Rendering text with SDL2 and OpenGL

I've been trying to have text rendering in my OpenGL scene using SDL2. The tutorial I came across is this one Rendering text

I followed the same code, and I get text rendering fine. However the issue I'm having is that there is obviously a "conflict" between the OpenGL rendering and the SDL_Renderer used in the code. When I run my scene the text displays but everything else keeps flickering. The following gif shows the issue:

Any idea on how to overcome this while still just using SDL2 and OpenGL, not another library or anything.

Thanks