Ultimately, it looks like a stripped down Debian build. BIOS is for their proprietary systems; my laptop still has its BIOS after the install. There appears to be limited hardware recognition (including wifi adapters). I haven’t dug into it much to this point, and trust the Start9 team based on my limited trust circle. But I could dive into it if I had time.
I like SBCs too. Although I don’t have any RISC-V ones at this point, but I could check it out on an ARM SBC at some point.
I use the laptop because it was unused, has sufficient tech, has a decent battery, and other laptop benefits.