Good call, you have reminded me.
2000ish I built a MAME machine and cocktail cabinet (very similar to this one) around an old pentium. It was approx 90% finished, as in it plays games, has sound, buttons, joystick etc but I never got round to finishing off the cosmetic side such as a bezel to hide the monitor edges and some artwork for the front. It's currently buried under piles of magazines, and generally gets used as shelf when I can't think of any where else to put stuff.
So large a tidy and magazine recycle, and a RPi 4 conversion for the MAME cabinet sounds like a good isolation project. Should be more powerful and much less power hungry that its current incarnation, *and* it gives me a reason to order another Pi.