Other systems of racism can also tied to some sort of belief in separate origins - caste in India.
Ancient Fossil Evidence Outside Africa – Fossil remains predating the supposed OOA migration (~60,000 years ago) have been found in China (Dali skull, 260,000 years old), Greece (Apidima 1, 210,000 years old), and the Levant (Misliya jaw, ~177,000 years old), suggesting Homo sapiens or proto-sapiens were present outside Africa long before the mainstream migration timeline.
Genetic Discrepancies – Some non-African populations (e.g., Australo-Melanesians and East Asians) possess archaic DNA from unknown hominins not found in Africans, implying deep regional continuity rather than a complete replacement by recent African migrants.
Multiple Ancestral Lineages – The discovery of distinct ancient hominin populations, such as the Denisovans and Red Deer Cave people, suggests a complex web of interbreeding rather than a single-origin replacement model.
Stone Tool Continuity in Asia – The presence of advanced stone tools in Asia (e.g., at Jwalapuram, India, ~74,000 years ago) suggests technological continuity rather than a disruption expected from an OOA replacement event.
MtDNA & Y-Chromosome Inconsistencies – While mitochondrial DNA (mtDNA) is often cited in support of OOA, recent studies indicate that some deep-rooted Y-chromosome lineages (e.g., haplogroup D found in Tibetans and Andamanese) show ancient divergence outside Africa, inconsistent with a recent African bottleneck.
Early Human Artifacts in the Americas – Artifacts and footprints in the Americas (e.g., White Sands, ~21,000–23,000 years ago) suggest a much earlier presence of humans, challenging the late migration model and implying deeper population history.
Human evolution and migration were likely far more complex than a single, recent dispersal from Africa. The evidence supports alternative models such as multiregional evolution or earlier, undocumented migrations.
We are of course fully aware of much earlier migrations of pre-Sapiens populations of Erectus and probably others. There's no controversy there, except in believing that these populations were ancestral to the current population.
That Australo-Melanesian and East Asian people possess a small amount of genes from archaic populations is also not controversial. They have genes from Denisovans, no issue there, most people outside of Africa also have a little Neanderthal DNA. There also seems to be remains of some unknown earlier homo, again that is in no way contradicting an African ancestry (out of Africa). It simply means that we don't know where or when all earlier homo species were.
Exactly when the "final" migration out of Africa happened is still not entirely clear. If it is 60000 (earlier suggestions have been 50k and even earlier, which was proved wrong) of somewhat earlier isn't yet set in stone. That doesn't change the actual pattern.
White Sands and what / when immigration to the Americas happened is in this context extremely late and is really irrelevant.
At this point the main hypothesis is that there was an Out of Africa event, and that the migrating people to some extent interbred with earlier migrations (specifically Neanderthals and Denisovans, and possibly some other yet unknown split from the ancestors of the two latter). That there was an acquisition of those extra genes is something new from the last few decades, but this really has zero to do with supporting a multi-regional hypothesis. If nothing else, the genetic evidence when looking at DNA from people from absolutely any place in the world is so overwhelming that there's no question at all. We even see the pre-migration genetic bottleneck - two people from opposite sides of the world have less genetic variation between them than the genetic variation between two chimpanzees from different sides of a river in a single forest.
That is contradicted by the findings below.
Genetic Discrepancies – Some non-African populations (e.g., Australo-Melanesians and East Asians) possess archaic DNA from unknown hominins not found in Africans, implying deep regional continuity rather than a complete replacement by recent African migrants.
Multiple Ancestral Lineages – The discovery of distinct ancient hominin populations, such as the Denisovans and Red Deer Cave people, suggests a complex web of interbreeding rather than a single-origin replacement model.
MtDNA & Y-Chromosome Inconsistencies – While mitochondrial DNA (mtDNA) is often cited in support of OOA, recent studies indicate that some deep-rooted Y-chromosome lineages (e.g., haplogroup D found in Tibetans and Andamanese) show ancient divergence outside Africa, inconsistent with a recent African bottleneck.
If Homo sapiens left Africa ~60,000 years ago, why do we find fossils in China that are 260,000 years old? In Greece we found 210,000 years old fossils, and the Levant at 177,000 years old? These predate the major OOA migration and suggest independent regional evolution.
Non-African populations, especially Australo-Melanesians, carry archaic DNA not found in Africans. Where did that archaic DNA originate? It was not Africa. Again, this shows a regional continuity rather than a simple migration-plus-interbreeding scenario.
If an African bottleneck occurred, why do we see deeply divergent lineages like Y-DNA haplogroup D in Tibetans and Andamanese? These suggest lineages of non-African ancestry survived bottlenecks.
Stone tools in India ~74,000 years ago show no signs of disruption, contradicting the idea that a major migration replaced existing populations.
The OOA model does not fully explain this evidence. A more nuanced model including persistent non-African lineages is the only thing that makes sense.
I can't see anything in what you listed which is different from Out of Africa, plus a little intermixing with earlier migrations (e.g. Neanderthals and Denisovans, and potentially others). That would fully explain why you see some "old" DNA in some populations. It's still Out of Africa, again because 96-98 % of the DNA of any person on Earth is from a (relatively) recent exodus out of Africa. This is still extremely different from the older multi-regional hypotheses.