It's been known since around the mid-90s that the "ice-free gap" opened up too late to allow for humans to arrive before Clovis, and that Clovis-first was an untenable theory. However, it takes a long time for scientific consensus to work its way into textbooks and popular imagination. When I was learning about this stuff in school around 2005-ish, the textbooks still suggested the ice-free migration route, although coastal migration was suggested as a plausible alternative. Even as late as 2017, there's still a popularly cited anthropology writer (but not an anthropologist) who believes in Clovis-first and vociferously argues against pre-Clovis migration.
This family of theories has been around for a while, 1491 by Charles Mann discusses them extensively, and that book is from 2005. Reliable evidence is sparse though, so this could be a major contribution.
For more than a decade, evidence has been piling up that humans colonized the Americas thousands of years before the Clovis people.
It's actually been longer than that. The site at Monte Verde [1] in Chile seems to have been widely accepted as a pre-Clovis site nearly 20 years ago (1997 according to Wikipedia [2]). Awareness of the site, at least among the archaeological community predates that (1989 [3]). The first radiocarbon dates indicating a pre-Clovis origin for the site go back to 1982[4].
The idea that Clovis was not the earliest culture in the Americas, and the commensurate theory that the earliest colonists must have been traveling by boat [5] goes back decades. I know I've been reading about it (in the popular press no less) since the 1990s. It seems like every article I read about it makes it seem like some new and revolutionary idea. The only conclusion I can draw is that archaeological science operates on time scales only slightly shorter than those the archaeologists study.