Flip Flappers should be available on /AM/ in its entirety at all times.
I attempted to reverse engineer >>/26990/ and >>/30902/ and combine it with some of my earlier saved instructions since they didn't really work for me and I finally got this to work on linux
ffmpeg -i input.mkv -vf subtitles=input.mkv -sn -c:a libopus -c:v libvpx-vp9 -b:a 128k -b:v 0 -crf 32 -deadline best -threads 12 -pass 1 -an -f webm /dev/null && \
ffmpeg -i input.mkv -vf subtitles=input.mkv -sn -c:a libopus -c:v libvpx-vp9 -b:a 128k -b:v 0 -crf 32 -deadline best -threads 12 -pass 2 output.webm
For windows change '/dev/null' to 'NUL' and '\' at the end of pass 1 line to '^'. Change -threads count to however threads of your CPU you want to employ for encoding.