As an enjoyer of fringe content it is pretty common lore that the Vatican is involved with UFOs

The testimony comes from a highly credentialed intelligence whistleblower that came to Congress to basically say "there's a money black hole sucking up the defense budget and no one knows about it because it's for black projects, and oh yeah UFOs"

Fun fact, in addition to that Pope Francis made a comment saying he'd baptize aliens:

"Who are we to close doors? In the early Church, even today, there is the ministry of the ostiary [usher]. And what did the ostiary do? He opened the door, received the people, allowed them to pass. But it was never the ministry of the closed door, never."

and from Grusch's claims (Wikipedia)

"documents reporting a spacecraft of alien origin had been recovered by Benito Mussolini's government in 1933 and procured by the U.S. in 1944 or 1945 with the assistance of the Vatican and the Five Eyes alliance. "

But I don't think there's any actual trail for hinting a pope saw an UFO sadly