Hi thank you for your reply.. I meant I had the same original error of “Warning Kernel.346541: eth-Rtl: Initialization failed network failure, ask for help via LCD”.
I had mine connected to a screen and keyboard too and it stops at this error and doesn't boot up.

When I first had it like a year ago it just had some printhead errors and which I solved by replacing the Hp11 printhead and skipped the alignment check by printing in monochrome. it worked fine for a while and we left it on as recommended but for long time, about 6 months without use. Now when I tried to reconnect it to the computer through a hub it give me the above kernel error while booting up. and on the LCD screen it says network initialization error. I also started hearing humming noise from the CPU.

So that's where I'm stuck right now. I hope it's not a complete motherboard change like you said.

Thanks
Mo Abdalla