Do you think it’s healthy to change yourself in order to be more attractive to potential partners?

If that is the only reason, no. However it is totally valid as one of the reasons if that makes sense.

Like... I lost weight primarily for my health and happiness but becoming more attractive to other humans is a big bonus incentive.

No. You should change yourself for the sake of bettering yourself or finding personal feelings fulfillment. If that action attracts a partner [or deflects someone incompatible] - all the better!

Sometimes. But I don't think that changing yourself for others will motivate you as much as wanting to change for yourself.

I guess that would depend on the change. If someone’s quitting hard drugs because nobody they want to spend time with finds being in a haze of high attractive maybe. But the hope is there’s more motivation for healthy changes than just others will like me