4.1 amp parasitic draw - 2020 Ford V-10 Thor Outlaw

You're stereo probably pulls some power even when off. TV antenna amplifier might be on and pulling some power. The control board in a gas refrigerator uses some power all the time. LP leak detector and CO detectors use some power.
Doesn't the inverter have an "off" switch? If not, you could install one as suggested in the battery cable. It really should have at least a fuse in the positive battery cable. Replacing it with a circuit breaker would make it easier to turn on and off.