The Steam Machine is slightly bigger than a portable Blu-ray / DVD player. (I just checked this with my own players)
I can’t wait for someone to make the equivalent of the Gamecube’s GBA Player for discs. Because of its size, It could even be a plastic shell where you put an existing Hitachi/LG portable drive without having to disassemble anything
I’m also still adapting to discussing other hardward in a community called steamdeck. I understand why, just still adjusting personally