SOP8 SOIC8 Test Clip and CH341A USB Programmer Flash for Most of 24 25 Series BIOS Chip with PDF Tutorial

Honestly have no idea, this is more of a hobby for me and I've never worked on one of those boards. That USB could be connected to anything (or nothing). If you do wire straight to it, make sure the voltage is right (really that goes for anything). UART or JTAG is usually one thing people immediately look for as an easy way in, but it helps to identify which chip holds that Linux image in the first place. Search for the numbers on each of them and try to find a datasheet, or even like a digikey product page. One of them should be something like "non-volatile flash", "nand flash" or "nor flash". If it's one of the 8 or 16 pin chips, it may be as easy as using a SOP8 or 16 test clip. Doesn't even need soldering. If you haven't identified that chip yet, I'd look for that as the next step. Edit: as opposed to non-volatile flash that would hold the linux image, you may find something like "DRAM" or "volatile flash". That's the RAM memory chip that's lost on restart.