I've recently purchased a Type-C to 2.5x5.5 cable to run a NUC with a small GaN adapter instead of the original big brick. It will take Type-C PD as input (max 100W) and provides 20V as output. You could probably somehow combine this with a HDPLEX DC-ATX (for normal ITX boards) or get a mini PC like a NUC or DeskMini with 2.5x5.5 DC input...
but I would be very, very careful that your setup is not exceeding the power output capabilities of your monitor else you might fry it...
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