There's actually a lot of interesting science around plant "mentation" for lack of a better term, stuff that's actually super scary if you stop to think about it.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3405699/

"Plants emit volatile organic compounds (VOCs) as a means to warn other plants of impending danger. Nearby plants exposed to the induced VOCs prepare their own defense weapons in response."

https://www.discovermagazine.com/planet-earth/is-plant-communication-a-real-thing

"Lilach Hadany, a professor at Tel Aviv University’s School of Plant Sciences and Food Security, wanted to better understand whether plants use the acoustic realm of communication, too.

In a study published this year, her team put tomato and tobacco plants in an acoustically isolated box and then recorded any ultrasonic sounds produced between 20 and 150 kilohertz. They experimented with cutting stems or leaving them without water as if to simulate drought.

The researchers found that the plants emitted popping and clicking sounds at around 60 decibels, approximately as loud as human chatter. These sounds were at an ultrasonic frequency that humans cannot naturally hear, however."

https://www.newyorker.com/magazine/2013/12/23/the-intelligent-plant

"Plants are able to sense and optimally respond to so many environmental variables—light, water, gravity, temperature, soil structure, nutrients, toxins, microbes, herbivores, chemical signals from other plants—that there may exist some brainlike information-processing system to integrate the data and coördinate a plant’s behavioral response. The authors pointed out that electrical and chemical signalling systems have been identified in plants which are homologous to those found in the nervous systems of animals. They also noted that neurotransmitters such as serotonin, dopamine, and glutamate have been found in plants, though their role remains unclear."

Ecological Vegans: A pound of animals tends to take 10 lbs of plants to sustain. Also other animals need these resources so using the smallest lowest impact sources to supply ourselves with food makes it more "ecologically vegan"

That said I don't think jellyfish have any kind of intelligence we can sympathize with so anti cruelty vegans as far as we know can eat jellyfish unless some scientific breakthrough is made.

There's a great old radiolab that covers and critiques 'plant intelligence' but afaik plants are no more intelligent than your immune system - they have some kind of stimulus memory but nothing resembling human logic or sensation

So some Asian cultures do eat jellyfish. Maybe this is a gotcha question or maybe it's just someone coming from a less eurocentric background.

Jellyfish are consumed as food in some parts of the world. I think the question may come from the fact that there's always some articles around about how jellyfish may be the food of the future, since they can be grown at sea (reducing land use) and don't require feed beyond algae, which is great from both an environmental and resource management perspective. I'm not sure it's entirely a cynical gotcha question :)