[Albion Wilde]

While I am not disputing that Mahoney may have been gay, he does not seem to have been out, definitely did not want to be out, and was not claimed in numerous obits to have had a partner. His New York Times obit does not mention any gayness, but does allude his claim that because of a colostomy, he avoided sex:

John Mahoney, Actor Best Known for ‘Frasier,’ Dies at 77

Here is the obit from the Hollywood publication, Variety, which also does not claim he was gay:

‘Frasier’ Star John Mahoney Dies at 77

So, what is your source, Peter Blood?

[Captain Peter Blood]

All I can say is that I recall seeing something about it when he died, that’s all.
It could be he was just a conformed Batchelor. It matters not really.