Recently I stumbled across a second hand behringer 602 eurorack mixing desk for about £20.
It's tiny, has all the inputs you can want, 3band eq, and stereo outputs for headphone, din (tulip), jacks etc etc.
There are several brands offering little 4-6 channel mixers like these for less than a set of strings.
It's slightly larger than an Ashdown pedal, so easy to stow, fit on a desk or on a bookshelf. Or schlep it to rehearsal or gigs (for your in-ear monitor, should you be so inclined).
Honestly the smartest twenty quid I've spent on a hobby.