It’s likely CentOS 7.9, which was released in Nov. 2020 and shipped with kernel version 3.10.0-1160. It’s not completely ridiculous for a one year old POS systems to have a four year old OS. Design for those systems probably started a few years ago, when CentOS 7.9 was relatively recent. For an embedded system the bias would have been toward an established and mature OS, and CentOS 8.x was likely considered “too new” at the time they were speccing these systems. Remotely upgrading between major releases would not be advisable in an embedded system. The RHEL/CentOS in-place upgrade story is… not great. There was zero support for in-place upgrade until RHEL/CentOS 7, and it’s still considered “at your own risk” (source).

I’m sure there would be a way to do this with Debian, but I have to confess I don’t know it. I have successfully done this in the past with Clover Bootloader. You have to enable an NVMe driver, but once that’s done you should see an option to boot from your NVMe device. After you’ve booted from it once, Clover should remember and boot from that device automatically going forward. I used this method for years in a home theatre PC with an old motherboard and an NVMe drive on a PCIe adapter.

Containourboros!