As far as I understand, most thin clients nowadays are just PCs, usually AMD embedded SoCs with very good support for Linux.

> Can you run Linux on a thin client?

Yeah, these originally came preloaded with eLux.

https://www.unicon.com/elux

> Also where did you buy them for so cheap?

Second hand on Ebay, I'm located in Europe.

This person has had success with the idea: https://weisser-zwerg.dev/posts/dell-wyse-fujitsu-futro/

No problem running lightweight distros on them, though the really thin clients tend to be underpowered for web browsing. Available very cheaply on ebay, and pretty much all support remote boot so easy to run diskless (assuming some minimal local server).

2Ws require a specific fabrication process that will take a while longer to ramp up (due to the RAM-in-chip)