Android has been able to do this for years - here's video with details of someone using an android phone as a desktop replacement - with an external monitor and keyboard, etc...:

https://www.youtube.com/watch?v=bB-icTl2J-c

Also, ChromeOS is a functional replacement for Windows + Office: ChromeOS + Google Docs. It comes on hardware (ChromeBooks or ChromeBoxes) which are very cheap but capable, because ChromeOS is very lightweight. These devices are on par, cost wise, with a Windows Terminal - and require even less IT dept. effort to maintain.