Perhaps, I dare say, a key indicator of sentience is the ability to kill another species, even its own, but chooses not to.
Sentience is awareness of one's surroundings. Your cat is sentient. Most embedded systems are to some degree sentient. We know what makes this - adequate interfaces to adequate sensors, plus some mechanism to respond to the input in some way. That's basically all it takes.
Sapience is the awareness of one's own mind - the ability to watch yourself think. We're pretty sure that your cat is not sapient, and neither are embedded systems. But we don't know what enables or causes sapience, nor how it does so.
So when we're talking about "consciousness" or something, we have to be clear whether we're talking about sentience or sapience. (And the conversation won't be using my words, so don't go by that - you have to sort out which idea is being discussed.) And of course the worst discussions have different people using the same word for different ideas, and nobody recognizes it, so the discussion is really about different definitions of the same word.
And, credit where due: I stole the term from Howard Tayler's wonderful "Schlock Mercenary" webcomic. It may not be original with him, but that's where I got it.
So like, a microcontroller deciding to turn on a LED from time to time when it feels like it is sentient? Sounds like it by that definition.
> a key indicator of sentience is the ability to kill another species, even its own, but chooses not to
Oh no. This appears to be a different definition now! I'm afraid I don't meet the sentience threshold then. I have many skills but I don't think that I have the ability to kill another species. Not alone at least.
It's very difficult to just walk down the street without killing half a dozen bugs.