hmm it looks like chatgpt forgot to add converting to SDR, you might need to add this extra flag to the command. also i made a mistake in that previous command, replace that "-i input.mp4" with that proper mp4 file path i put near the beginning, here's the full example command:
ffmpeg -i "C:\Users\Admin\Downloads\Star.Wars.Episode.I.The.Phantom.Menace.Extended.Edition.x265.HDR.2160p-v2-NumeralJ-2.mp4" -ss 01:30:10 -t 20 -vf "scale=1920:804, zscale=t=linear:npl=100, format=gbrpf32le, zscale=p=bt709, tonemap=tonemap=hable:desat=0, scale=1920:804" -c:v libvpx-vp9 -b:v 0 -crf 31 -pass 1 -an NUL && ffmpeg -i "C:\Users\Admin\Downloads\Star.Wars.Episode.I.The.Phantom.Menace.Extended.Edition.x265.HDR.2160p-v2-NumeralJ-2.mp4" -ss 01:30:10 -t 20 -vf "scale=1920:804, zscale=t=linear:npl=100, format=gbrpf32le, zscale=p=bt709, tonemap=tonemap=hable:desat=0, scale=1920:804" -c:v libvpx-vp9 -b:v 0 -crf 31 -pass 2 -c:a libvorbis -b:a 96k output.webm
you know how to use command prompt and how to navigate around with it (using 'cd' command), right? to get to your folder where you downloaded ffmpeg.exe (e.g. cd "C:\Users\Admin\Documents\ffmpeg"), so then you can run that command. and to paste using right-click.
https://www.gyan.dev/ffmpeg/builds/ffmpeg-release-essentials.zip (you only need ffmpeg.exe from the bin folder)
and if you look carefully there are two instances of "-crf 31" you need to replace both of them when adjusting crf since it's two-pass encoding. same with the timestamp where you'll trimming starting from to make the 20 sec clip.
