Lightning blast question

overcharge and hypercharge passives say they will not trigger if channeled

does keeping the button pressed count as channeling? or do they refer to some other passsive that makes it a channel spell?

The channelling refers to the “Insidious Conduction” Keynode at the bottom left, that transforms LB into a channel skill.

It never does. Keeping the button pressed just means you’re casting it over and over again, but if you simply click fast enough, you achieve the same result.
Channeling is for skills that require having the button pressed, like warpath, disintegrate, etc. (and any skill where you take a node that says that the skill is now channeled, like wandering spirits).