You can try the ffmpeg custom output settings I posted here:
Hi All, I would appreciate your thoughts. I am a trader and am needing a solution to record a day's worth of trading. I use 3 4k 43" screens with NVIDIA Quadro per desk. These show many graphs/charts of live market data (but no video content). At the end of the day I just want to extract and...
obsproject.com
I'm able to successfully record my ultrawide 5120x1440 screen with it.
However, this is of limited usefulness, because almost nobody else has a monitor with such an aspect ratio (32:9). If you intend to share your footage, keep in mind this will be usually watched on monitors with aspect ratio 16:9, i. e. half width, i. e. half of the screen is occupied by the black bars at top and bottom.