Probably underpowered for your needs, but within a year or two I am expecting used Chromebooks to be up-to-date enough to include the current Linux (e.g. Debian

Probably underpowered for your needs, but within a year or two I am expecting used Chromebooks to be up-to-date enough to include the current Linux (e.g. Debian) support. So perhaps $50 and will include keyboard, screen, and ca 5W idle consumption.