The XYFB manual contains a ritual for flushing sediment. It will tell you to attach a garden hose to the drain valve. What it won’t tell you: that plastic valve will snap off if you look at it wrong. The real feature here is “how to replace a broken drain valve without flooding your garage.”
(and its cousin, the XY-FA) is a mini tankless induction water heater that has become a bit of a cult object in DIY and RV circles. While it's marketed as a sleek, 3000W intelligent solution for instant hot water, the "interesting story" behind it often involves the reality of trying to run a high-draw appliance on standard household circuits. The "Interesting" Reality of the XY-FB xyfb water heater manual