The main impact would be philosophical and theological. Some religious beliefs about human uniqueness and "specialness" would be challenged. The discovery would become a beacon for future possibility. We would know that we are not alone in the universe and that existence and activity away from the protective atmosphere and gravitational pull of a comfortable planet is possible. We would also know that another civilization has accomplished monumental engineering feats that we can barely imagine, and that we have a very long way to go on the precarious path of scientific and technical progress. And we would know that there is a whole wonderful universe out there, awaiting our eventual arrival.
John G. Cramer's 2016 nonfiction book (Amazon gives it 5 stars) describing his transactional interpretation of quantum mechanics, The Quantum Handshake - Entanglement, Nonlocality, and Transactions, (Springer, January-2016) is available online as a hardcover or eBook at: http://www.springer.com/gp/book/9783319246406 or https://www.amazon.com/dp/3319246402.
SF Novels by John Cramer: Printed editions of John's hard SF novels Twistor and Einstein's Bridge are available from Amazon at https://www.amazon.com/Twistor-John-Cramer/dp/048680450X and https://www.amazon.com/EINSTEINS-BRIDGE-H-John-Cramer/dp/0380975106 . His new novel, Fermi's Question is coming soon from Baen Books.
Alternate View Columns Online: Electronic reprints of 212 or more "The Alternate View" columns by John G. Cramer published in Analog between 1984 and the present are currently available online at: http://www.npl.washington.edu/av .
References:
Kardashev Civilizations:
N.
S. Kardashev, "Transmission of Information by Extraterrestrial Civilizations",
(translation) Soviet Astronomy-AJ v8#2,
217-221 (1964).
Dyson
Sphere:
Freeman
J. Dyson, "Search for Artificial Stellar Sources of Infrared Radiation", Science
131, 1667 (1960) and "Artificial Biosphere", Science 132,
252 (1960).
Dyson Structure for Black Hole:
Tiger
Yu-Yang Hsiao, et al., "A Dyson Sphere Around a Black Hole", ArXiv
2106.15181v2 [astro-ph.HE].