I've got a non-smart washer, but after a recent power outage I noticed that it resumes the wash cycle at it's current point when power is cut then restored.

Enter an IKEA smart button and smart plug.

I load the washer, get it started then press the button to kill power and enable an automation (currently on have 4 am and 3 pm).

At 4am or 3pm, the automation turns the power back on and disables itself.

Next step is monitoring the smart plug power monitoring to send a notification when the washer finishes.