lux ults during stun

Her ult isn't channeled regardless of what the animation says. Once she presses the button even killing her won't stop it.

She cannot be stopped by cc but you can definitely kill her to stop it. Same with many other ults that have a visible windup animation like Ezreal, Nami, Sona.

this is because her ult is not considered a channel. cc stops CHANNEL ultimates, like pantheons, fiddlesticks, malzahar.

I main jinx and have gotten plenty of kills by being able to click R right before getting stunned so i can still do damage through the cc and not lose too much dps.

Lux ult just has a really long wind-up, regardless of displaces (knockbacks), stuns, silences, disrupts, etc. her ult will still go off as long as she cast it before the cc is applied. The same goes to Ezreal ult, Nami ult,. Killing her however will stop it as the windup requires her to be alive to finish.