Steam deck (LCD model) will, at no point, turn on unless plugged into charger or hooked up to the dock, regardless of how much battery is left. No response when trying to do things like booting into bios or anything else. Works perfectly fine when plugged in, docked to TV or standalone. No feedback at all, either, from buttons or trackpad haptics either when unplugged.

I've done a bios/firmware reset thing while plugged in and let that go for a while, following the advice of a Steam community forum (not sure whether the blinking power indicator thing is supposed to stop blinking when it's done, but I definitely let it go for longer than the forum post was saying). Went through the process of going through and enabling the main channel OS updates as well through dev settings and updating didn't fix it.

Have taken the backplate off and everything looks fine (I'm not an expert on mechanical things, though) and thankfully no spicy death pillow.

Any advice? At this point I'm even willing to back up anything important and do a factory reset if I have to. Also, if need be, I have a photo of the internals just in case I need to show it (again, not good with electronics on the hardware side of things).