That is a really big scam. I have heard of that system, it basically markets itself to protect the BIOS from cold boot attacks, however in reality this is just a mandatory access control that is out of your hands.
So it looks like you don't even own your laptop, since the laptop locks you out if you try to tweak it. It's truly horrible how scumbags these manufacturers are.
But hey, this is what the dumb customers want usually, they just want more trendy stuff, while not realizing how many side-effects these things are.
I am not talking about you, obviously many people are victims of this. But most people actually like this, so they are to blame.
What laptop or computer systems should I use that are open sourced, no closed source firmware?
There aren't any, that are fully open source. There is always some kind of binary blob there that is from the manufacturer and closed source.
But there are already endeavours to make them, via FPGA and other technologies.
Unfortunately these are still 5-10 years away.
https://en.wikipedia.org/wiki/Open-source_hardware