These scopes were actually made by Rigol, you can see their logo if you remove one channel shielding box. Agilent/Keysight does this a lot with their basic products lately. (So much for "premium" instruments). I encountered a similar issue like you - one day, the scope suddenly didn't boot. My screen worked however, it displayed the logo, buttons lit up, but then the scope froze. Is the screen really dead? Does its backlight work?
Anyway, I tried to un-brick "my" scope back then. The problem is, if the scope doesn't boot, you can't write new firmware. So my plan was to dump Flash contents from a working scope and write it to the bricked one. The scopes are based on Analog Devices ADSP-BF531 Blackfin DSP, so I borrowed an emulator to do that. But I quickly hit a wall, I could dump only about 1/4 of the Flash. The Flash is external and to access it, you have to provide the emulator with a specialized hardware configuration file. Normally, SW designers have to create it before they start their work, but of course I didn't have it. Plus, I've never used Blackfins and it would require reverse-engineering Flash addressing scheme. I actually knew a guy who could help, but he was quite busy and the scope simply wasn't worth our combined time to do it.
BTW, the scope also contains Altera EP1C6Q240C8N FPGA, but I don't think it has separate configuration Flash. I assume its contents are part of the main Flash firmware and it's configured from the Blackfin CPU once the CPU boots.