Why Am I More Gassy at High Altitudes?

https://outdoorsfaqs.com/why-am-i-more-gassy-at-high-altitudes/
If you feel that you fart more at altitude, there are at least two physical reasons for this:

Expansion of colonic gas due to the decreased atmospheric pressure at high altitude.
Gasses dissolved into our body liquids diffuse into intestinal lumen because of increased altitude.