If you don’t feel like carrying around big noise canceling headphones, try a smaller pair of in-ear headphones. Even a $20-40 pair like the Anker SoundBuds or Xiaomi Pistons will give a one-two punch of onboard comfort: the ear gels act as earplugs to reduce the background noise, and then your own sound drowns out the world even more. Cheap, small, disposable and indispensable for long travel.

re the original question, there isn’t much you can do - the poor loud snorer probably can’t control it, and short of an FA poking them every ten minutes, there’s not much they can do either. The best option is relocating yourself if able.