They came from Siberia, as demonstrated by many DNA studies that show relatedness with modern Siberians.

Humans certainly lived in Beringia, as evidenced by the occasional artifact that comes up in the nets of trawlers that fish above what was once exposed land during the last glacial maximum.

However, whether that migratory route went over land or by sea is currently something being debated and studied. Evidence has recently been published of human activity in the Americas between 16,000 and 20,000 years ago, including an encampment in Idaho that was very well dated in the summer of 2019.

At that time, over 16,000 years ago, a massive sheet of glacial ice stretched across the northern part of the continent (there were unglaciated refuges as well). It is very difficult to imagine how anyone could have crossed hundreds of miles of dangerous ice without any source of food or fuel along the way.

Because of this, some scientists speculate that the Siberians migrated along the east coast in seal skin boats along the "Kelp Highway," stopping in the occassional un-iced refuge and fishing and hunting for seals, otters, etc. along the way. Once south of the ice, some of them could have started moving inland.

The evidence for the timing and extent of the ice sheets is very well understood at this point. Geological formations are part of this, as are genetic studies of plants and invertebrates that we can see genetically bottlenecked in refuges from the ice before expanding into the previously iced-over land.

But the area of origin for modern Native Americans is not in doubt. They came from Siberia and DNA shows it.