Do Arahants experience non-neutral mental vedana?

Arahat will feel the physical pain. Say an Arhat steps on a pebble. This will b painful. He will not have the mental proliferation which adds to the physical pain because one is suffering about what happened mentally.

An Arhat will feel the pleasure of Jhana but this is purely mind born. I believe what Sallatha Sutta mentions is if one experience pleasure of pain physically this will not have a mental ripple of thoughts which are unpleasant or pleasant.

From MN121, where the Buddha discusses his current practice with Ananda, we have:

They understand: ‘This field of perception is empty of the perception of the defilements of sensuality, desire to be reborn, and ignorance.

There is only this that is not emptiness, namely that associated with the six sense fields dependent on this body and conditioned by life.’

In other words, the Buddha was fully aware of his present circumstances yet not burdened by craving, aversion or delusion. A meal would be a meal. A mosquito bite would be a mosquito bite. There would be no delusions that wanting more or wanting less would be of any value.

Note that "conditioned by life" does allow for things like avoiding peanuts if one is allergic or taking medicines such as insulin as needed. It also allows for cultural food preferences, since those are often tied to genetics. For example, some cultures tend towards lactose intolerance while others rely on dairy products and that "preference" is largely dictated by genetics. However, I find it really difficult to imagine any arahant expressing a preference for a frappuccino over a latte.

In the sutta, the Buddha stated that when encountering a painful physical feeling, due to aversion, an uninstructed worldling will generate a painful mental feeling. Now he has two painful feelings, instead of one.

On the other hand, the Arahant, when he feels painful or pleasant physical feelings, he doesn't have aversion or lust/greed, so he doesn't generate any painful or pleasant mental feelings. Also, he would not try to seek pleasure to distract himself from pain.

However, it does not say that the Arahant cannot generate pleasant mental feelings due to jhana. It is clear that the Arahant will not generate painful mental feelings because he is free from greed/lust, aversion and delusion. However, he can still generate pleasant mental feelings due to jhana and possibly also due to other non-greed/lust causes (e.g. metta).

In other words, the sutta only says that the Arahant does not generate painful or pleasant mental feelings out of painful or pleasant physical feelings. However, it does not imply that the Arahant will never generate pleasant mental feelings.

From SN 36.6:

“Bhikkhus, when the instructed noble disciple is contacted by a painful feeling, he does not sorrow, grieve, or lament; he does not weep beating his breast and become distraught. He feels one feeling—a bodily one, not a mental one. Suppose they were to strike a man with a dart, but they would not strike him immediately afterwards with a second dart, so that the man would feel a feeling caused by one dart only. So too, when the instructed noble disciple is contacted by a painful feeling … he feels one feeling—a bodily one, not a mental one.

“Being contacted by that same painful feeling, he harbours no aversion towards it. Since he harbours no aversion towards painful feeling, the underlying tendency to aversion towards painful feeling does not lie behind this. Being contacted by painful feeling, he does not seek delight in sensual pleasure. For what reason? Because the instructed noble disciple knows of an escape from painful feeling other than sensual pleasure. Since he does not seek delight in sensual pleasure, the underlying tendency to lust for pleasant feeling does not lie behind this. He understands as it really is the origin and the passing away, the gratification, the danger, and the escape in the case of these feelings. Since he understands these things, the underlying tendency to ignorance in regard to neither-painful-nor-pleasant feeling does not lie behind this.

“If he feels a pleasant feeling, he feels it detached. If he feels a painful feeling, he feels it detached. If he feels a neither-painful-nor-pleasant feeling, he feels it detached. This, bhikkhus, is called a noble disciple who is detached from birth, aging, and death; who is detached from sorrow, lamentation, pain, displeasure, and despair; who is detached from suffering, I say.