...Neither amph or meth has any appreciable serotonin release...
This is patently false. The recreational isomer of methamphetamine in particular is a 5HT releaser in a capacity that is FAR from negligible. This is easily confirmed from hundreds of studies on methamphetamines binding affinities. "Regular" (N-dihydro) amphetamine has negligible serotonin effects, this is true. Methamphetamine works on serotonin in a significant way, though. This effect quickly falls by the wayside once a major methamphetamine tolerance is established, however.
OP: I have the same problem - BUT (and this is a BIG caveat) - when I first was taking amphetamine as prescribed, almost 2 decades ago, amphetamine worked great at low dosages and had no dysphoria.
These days, anything under 60mg of d-amphetamine will just leave me irritable and CRAVING amphetamines. This is after years and years of abusing Herculean doses of various amphetamines and cathinones. There is a medical phenomenon known as "amphetamine sensitization". There are many changes in the way the brain reacts to amphetamines after this effect has manifested, but I will not go into all of them here. Look it up for a fascinating read. However, dysphoria from low doses of amphetamines like you describe is one of the things this effect can cause. How long have you been using amphetamines? What diagnoses do you have, and what other pharmaceuticals and supplements do you take?
Amphetamine sensitization is almost exclusively induced by recreational abuse, but also sometimes from proper usage for a VERY long course of therapy. It is now the major consensus among most psychologists, psychiatrists, and neurologists that amphetamine therapy [for psychiatric maladies, at least] should include at least one "vacation" day per week, where the the patient does not take their prescribed amphetamines.
One promenint theory involves TAAR1. Amphetamine is a major ligand for TAAR1, in addition to things like the DAT and NET. In theory, the TAAR1 receptor, which is believed to play a role in whether a compound is a monoamine releaser or merely a reuptake inhibitor, has a "breaking point". By this, I mean that after a certain amount of activation, an irreversible change occurs.