Cannot answer about preamps, however, for any single MM input you can buy an external SUT that has front selectable inputs, and PASS for MM.
mine, Fidelity Research FRT-4 has 3 inputs, adjustable impedance, PASS
this is a good price these days
other FRT-4's available
https://www.hifishark.com/search?q=frt-4
Entre-100 also has 3 inputs, front selectable, and a few optional impedances and PASS
https://www.hifishark.com/search?q=entre-100