For a while, and I think even still today, the cheapest linux thing you can buy that has USB ports, wifi, and a power adapter are those Rockchip CPU powered Android TV boxes that are super popular from aliexpress and the like. There were people getting pretty mainline Linux distros on them. They have all moved on to be more expensive now (with 8GB RAM and way more cores than needed), but if you look back at ones from a few years ago you can find ones that were 1GB or 2GB of ram with a bit of eMMC storage and a quad core arm CPU roughly equivalent to a Raspberry Pi 3 in performance. Unlike a lot of these linux microcontroller-sized boards, you got power, wifi, usb ports, an audio out, and a nice case for it. What you lack is exposed GPIO usually. At one point you could find them for around $24. I think you still can if you look hard enough.