Well, Discord decided to lower the free tier file limit to 10Mb.
Challenge accepted.
ffmpeg -i deerfox.mkv \
-t 0:31:00 \
-pix_fmt yuv420p10le \
-vf scale=-2:360 \
-c:v libvpx-vp9 \
-pass 2 -b:v 30k \
-maxrate 35k \
-threads 1 \
-tune 1 \
-tune-content 2 \
-speed 0 \
-tile-columns 0 \
-frame-parallel 0 \
-auto-alt-ref 1 \
-lag-in-frames 25 \
-keyint_min 9999 \
-g 9999 \
-aq-mode 0 \
-c:a libopu\
-b:a 10k \
-vbr:a constrained \
-map 0:v:0 \
-map 0:a:1 \
-ac 1 \
-f webm \
out10mb.webm