I know everyone's talking about specifics and this may be a no-brainer but how about this "proof" that interactions between humans and alien intelligences occur. Be interesting to see what people think.
1. From UFO (UAP) reports as detailed in say, Leslie Kean's book an alien technology is operating around/on Earth.
2. Any alien intelligence will be either millions of years older or younger than us due to the age differences of stars (assuming they are from our physical universe as a default).
3. From 1 they are older and also technologically.
4. To assume they have "just arrived" pre-selects our present "intelligence epoch" (say the last 150 years when we’ve had electrical/nuclear technology) as special which is unjustified.
5. To be here, over at least a minimum of several centuries (but realistically at minimum thousands of years from 1 and 2) implies some kind of program - which could be many!
6. To utterly ignore the most intelligent species on Earth over, say millennia, is untenable.
7. Close interactions between aliens and humans occur and because of the technology mismatch only under their control.
8. If 7 Is correct one can suggest that any interactions cannot but be for biological or related reasons as the mismatch in intelligence precludes other reasons (but I don’t rule out, in some form, educational).
I think 1, 2, 3 and 4 cannot be refuted if one is truly open to the data. But together they imply 5 and 6 from which 7 follows. 8 is speculative as we have to guess what they are up to.
To add some meat to this is a paper from two clever fellows that solves the distance problem to do with spreading of alien intelligences over vast distances.
Eternity in six hours: intergalactic spreading of intelligent life and sharpening the Fermi paradox
http://www.fhi.ox.ac.uk/intergalactic-spreading.pdf