So, until this last update, choosing fullscreen or windowed borderless would present the game in stretched, with no option to go for black bars instead. Now fullscreen show the game in 16:9 with black bars, which is exactly what I want. I like this monitor not only for its resolution but also color fidelity and the 240hz. Playing it windowed has been making my experience worse in every sense, and in desperation I used to play on my second monitor (144hz) and to move my peripherals around everytime I played Valorant. Either option was not optimal, so thank you for finally finding a solution for this!