ISTR that Wyse Technology (fond memories of their WY-60 terminals) made thin clients out of Raspberry Pis.
Stratodesk makes them now:
https://www.stratodesk.com/solutions/raspberry-pi-thin-clien...
How Good is the new Raspberry Pi 4 as a Thin Client? (2019)
https://www.stratodesk.com/how-good-is-the-new-raspberry-pi-...