Having same issue here. Checked it myself and sound is working, so the game is running without renderer. Tried to find some clues on the cause itself. As my knowledge is far below from what would be enough to even consider tackling it myself(yet to pursue my first degree without prior knowledge, but am good in solving some problems in various unknown fields 😓), I've dug up something that might be of use:

https://discourse.libsdl.org/t/black-screen-after-ubuntu-update-from-18-04-to-20...

https://discourse.libsdl.org/t/sdl-renderer-calls-from-different-thread-possible...

It might be hit or miss but guess it's better to leave it here rather than do nothing.

Again, sorry if what I've wrote has nothing to do with this, as I'm still learning. Guess, I just like to make sense of what's a total gibberish for me (pls, don't kill me) :P

Thank you, that did it!