Sorry, it isn't 100% clear if the power controller is the NUC or separate, or if you have access to run your own code on the NUC. (Maybe it was clear to everyone but me.)
Relying on the Windows sound theme doesn't seem too reliable.
I still haven't seen the definition of "booted" yet. That would seem to be a fairly important part of this.
One way to make sure the NUC is booted is for it to control power to everything else so it has to boot before anything else even turns on... for some values of "NUC is booted".
-- Rick C. + Get 1,000 miles of free Supercharging + Tesla referral code - https://ts.la/richard11209
Plug a UART bridge into one of the USB ports and send some message over that upon booting
on linux sleep 0.1 < /dev/ttyUSB0
Will put a 100ms pulse on the RTS and DTR pins.
-- Jasen.
Externally USB and HDMI/DisplayPort, Ethernet, and maybe analog audio, internally SATA, M.2 and other PCIe variants, (often) Serial port header, and SMB if you know where to solder.
-- Jasen.
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