Black screen after Ubuntu update from 18.04 to 20.04

My program worked well on Ubuntu 18.04 with SDL2. On Ubuntu 20.04 I installed SDL2 with ‘sudo apt install libsdl2-dev’ which is version 2.0.10 - window is completely black (sound is still coming out though). Tried build/install from sources and SDL_VERSION shows 2.0.13 (for both compiled and linked) - same black screen.

I use SDL2 this way:

if ( SDL_Init( SDL_INIT_VIDEO | SDL_INIT_AUDIO ) < 0 ) {
    cerr << "Failed to SDL_Init()" << endl;
    return -1;
}
SDL_Window * sdlWindow = SDL_CreateWindow(
    "SDL window",
    SDL_WINDOWPOS_UNDEFINED,
    SDL_WINDOWPOS_UNDEFINED,
    1280, 720,
    0
);
SDL_Renderer * sdlRenderer = SDL_CreateRenderer( sdlWindow, -1, 0 );
const auto sdlTexture = SDL_CreateTexture(
    sdlRenderer,
    SDL_PIXELFORMAT_BGR24,
    SDL_TEXTUREACCESS_STREAMING,
    1280, 720
);
 ... and then when I have bitmap data:

SDL_UpdateTexture( sdlTexture, NULL, bitmap_data.data, bitmap_data.linesize );
SDL_RenderClear( sdlRenderer );
SDL_RenderCopy( sdlRenderer, sdlTexture, NULL, NULL );
SDL_RenderPresent( sdlRenderer );

What could be the reason? Thanks in advance.