The trolley problem is probably the most famous thought experiment in ethics, but it doesn't do a good job of distinguishing ethical theories. Both utilitarianism and Kantian deontology agree that it's correct (or at least permissible) to flip the switch. The Kantian argument is that you are not treating the one person merely as a means—you save the five via the second track, and they would still be saved even if the one person wasn't present.

There's a sort of intuitionist deontology that says it is wrong to ever perform an action that causes someone to die, but only 13% of philosophers[1] say you shouldn't switch, compared to 63% who say you should.

[1] https://survey2020.philpeople.org/survey/results/4922