Non-serotonergic hallucinogens

According to this article, agonism of the 5-HT$_{2A}$ is necessary for hallucinogenesis. Now, not all hallucinogens are primarily serotonergic, but does there exist hallucinogens that aren’t at all serotonergic? If so, that means there are hallucinogens that don’t agonise the necessary receptors for hallucinogenesis.

Would that mean that these non-serotonergic hallucinogens only produce visual distortions (illusions), and not "true" hallucinations? And do all serotonergic hallucinogens activate the 5-HT$_{2A}$ receptors, or are there serotonergic hallucinogens that don’t activate exactly this receptor, but still primarily or partially operates on all the other serotonergic receptors?