powercfg –lastwake my computer woke up from sleep for the following reason:
Wake History Count - 1 Wake History  Wake Source Count - 1 Wake Source  Type: Wake Timer Owner: [PROCESS] \Device\HarddiskVolume4\Program Files\Oracle\VirtualBox\VBoxSVC.exe
According to https://windowsreport.com/windows-8-windows-10-wakes-sleep-fix/, if I click on the Power Management tab I can uncheck "Allow this device to wake the computer" to prevent the device from waking my computer up again.
Only problem: I don't have that tab!:
Some of my network adapters have it (my physical network adapters), but not the one that woke my computer up.