George Kwast spent 15 years mostly alone in his apartment in Manhattan after he retired in 2009, reading, watching television and thinking about friends who had moved away or died.

Then he visited the Edie Windsor SAGE Center, which relies on a mix of private and public funding to provide services for older L.G.B.T.Q. adults, who face far higher rates of isolation and poverty than their heterosexual peers.

Since that day last year, Mr. Kwast’s life has changed. He has new friends who invite him to dinner parties or join him at the center for book clubs, bingo and karaoke nights. He performs midcentury hits by Irving Berlin and Perry Como.

“I need to dance around too, because I am really more an entertainer than a singer,” said Mr. Kwast, 76, who worked for 30 years as a hotel waiter. “Last week I sang Doris Day, her version of ‘Enjoy Yourself (It’s Later Than You Think).’”

But the Edie Windsor center and other L.G.B.T.Q. social service organizations now face a threat to their existence from the Trump administration, which has paired a zeal for aggressive budget cuts with an undisguised hostility toward diversity programs and the transgender community.

The most immediate danger stems from executive orders that President Trump issued soon after taking office in January, which barred federal contractors like the center from using diversity, equity and inclusion policies.