Star Trek: 10 Secrets Of The Q Continuum
9. They Disappeared For At Least 600 Years
The Continuum visited Earth many times before formally introducing themselves in Encounter At Farpoint. Quinn alone visited Issac Newton in the 17th century, Will Riker's ancestor Thaddius Riker in the 19th century, and a famous musician named Maury Ginsberg in the 20th century. After meeting Picard, Q became a regular nuisance in Starfleet.
In the Discovery episode The Examples, set in 3190, the crew was discussing possible candidates for the creators of the DMA, and we learned that the Q Continuum had not made contact with Starfleet for 600 years, or since roughly 2590. Q's death in Star Trek: Picard was in 2401, so this shows that other members of the Q Continuum continued to visit Earth after John de Lancie's Q died, but decided to stop for some reason after the 26th century, perhaps waiting for humanity to cross some threshold, or simply manipulating Human history in hiding, like they did before Q introduced himself to Picard.