thanks for the reply.
So when I used splore, and went to the carts directory, and pressed on "Umbra", I got "Could not load" u_u,
So.... it seems that trying to update pico-8 to a handheld was a fool's errand. after attempting to update pico-8 from 0.2.6b to 0.2.7 caused pico-8 to no longer work at all. and updating to Gladiator II was no good either. Pico-8 just does not want to run on Knulli. luckily, I have a 35xxSP that runs MUOS (Pixie) and I was able to easily update Pico-8 to 0.2.7. and... I can now run the demo. Also, with the windows version, I'm also able to run it on my PC and Android handhelds running Gamehub lite. so it's all good. thank you for walking this extra mile with me. I look forward to what you have for us in the future...
quick (silly) update. I was able to get pico-8 upgraded on my CubeXX running Knulli (Gladiator II) after all. I was dumb, I forgot that Knulli has an awesome feature of just copying the raspberry pi .zip file for pico-8 and do a system install of it. and then "Robert's your mother's brother", it all works. Umbra is running on it. I hope that this hopes some other poor soul in the future!
PS, AI is not your friend in this case, but Discord is! :)