A few months ago, I ripped the guts out of my old Bush valve radio and installed a Pi with HifiBerry AMP+ , dietpi and Dynavox speakers.
I made a baffle to mount the speakers that was the same dimensions as the old speaker baffle but I had to build a frame around the edge so that the new (guitar amp) cloth would not touch the front-mounted speakers. (the original speaker was mounted behind the baffle).
I tried to get a rotary encoder to work to control the mixer volume but it didn’t seem to accurately sense the direction of rotation so I switched to plan b and installed an old USB IR sensor and blew the dust of an old remote control. Now buttons 1-9 play various internet radio stations and the volume up and down buttons control the volume. Sweet.(the knobs on the front current do nothing at all).
I have Spotyconnect installed so can plan to it from spotify from my phone and of course (when not doing either of the above) it works as a Roon endpoint just fine.
I plan to install some leds to back-light the tuner display (the leds I had had the wrong forward voltage so will need to buy some new ones).
I’m very happy with it and I like the sound very much (in the context of what it is and it’s intended purpose).