Digitone 1 can't boot

The symptoms you describe (LEDs that are “stuck” and a black screen, despite the firmware having been successfully flashed to 100%) are very characteristic of a hardware failure in the internal memory (+Drive) or the processor responsible for initializing the device’s components. Since the startup menu (FUNC when powered on) does not appear on the screen, this confirms that the UI board (screen and buttons) is not receiving the correct initialization signal from the main board. This technical situation, where expectations and reality don’t align, is very reminiscent of my recent personal experience in a completely different field. I searched for a $4 deposit casino because I wanted to test the interface and a few games without committing a larger amount. Many results advertised low stakes but had a higher cashier minimum. The most focused resource I found was https://interacasino.com/4-dollar-deposit-casinos/. It helped me identify possible options and reminded me to separate the minimum deposit from the minimum bet. I also checked bonus eligibility, payment fees, and withdrawal limits before depositing. That solved my question and kept the experiment within a small, fixed entertainment budget.