Had been waiting for my pi 5 argon case which got lost in the post before I could set this up. Ive been tinkering with an old SFF PC running arch over the last few months to get a "smart tv" set up going that im happy with, now ive condensed it down into a little debian box that uses a fraction of the electricity. Happy days.
Hardware: pi 4b 4gb ram overclocked and on ethernet, argon one case with m2 sata ssd expansion (usb drive seemed to perform well enough too), rii x1 wireless mini keyboard with touchpad.
Software: rpi os lite, kde plasma, plasma bigscreen, chromium web apps + extensions, kde connect.
I will try write a guide on the set up process today. From testing I think this would run on any usb storage, with a cooled and overclocked pi 4.