There is zero evidence of ETs visiting Earth. By evidence I mean testable, verifiable evidence.
Perhaps you're confusing "verifiable" with "verified", because this is overstatement. Even for you.
Consider for example the Barney and Betty Hill abduction story, and Betty Hill's "star map". Carl Sagan and students of J. Allen Hynek, among others, attempted to scour stellar databases looking for an alignment of stars that corresponded to Betty Hill's drawing. This is a good example of how real science can be done based on personal stories. In this case, there as no corroboration of the Hill's drawing. And there are some fundamental epistemological problems in the effort (human memory being unlikely to accurately recall distances and spatial relationships, and of course the unlikeliness that the perspective of any random "star map" would match anything we have). But this is verifiable in principle.
The same could be said for all sorts of reports. This is why a central database of reports is needed. For example, if there were other reports of "star maps" that were similar to Betty Hill's, that would be a really interesting fact to explore. No one knows this though because the very basic science hasn't been done, so the data is not collected or collated or accessible. This is why GEIPAN's recent efforts to make a "data warehouse" of all existing report databases is so crucial to the science of UAP reports.
Probably my favorite report is the RB-47 UFO from 1957. The RB-47 at the time was the most sophisticated spy plane in operation, and could be outfitted with up to 600 sensors and cameras for some flights. While this was a training flight, it is still likely that the RB-47's radar cameras were operational (these were needed to review radar data when the RB-47s invaded Soviet airspace and sucked up data about anti-aircraft systems from the Soviet response). If such data existed, it probably would have been going to NSA anyway. It's well attested that USAF Blue Book was essentially a PR effort and pretty low-level (much of it wasn't even classified). God only knows what the NSA does with data from UFO reports.
Now this is an example of a case where there are good reasons to think better physical data existed. That data is inaccessible to you and me, and perhaps had been destroyed. But again, in principle this is absolutely verifiable. Particularly given the testimony about calibrating the ECM and radar with known sources during the encounter. If the physical reality of the RB-47 report were established factually, that would lend considerable weight to the ET visitation hypothesis since it would be the best available explanation. In the case of more controversial "abduction" or "contact" reports, establishing patterns between reports could actually yield more direct evidence.
TL,DR
"Verifiable" means "verifiable in principle", not "positively verified in practice" or "easily verifiable in practice without doing some difficult science".