There are several synonyms, like 'it's a complex matter' or 'it's a convoluted tale'.
Well, 'it's a long - winded narrative' and 'it's a lengthy yarn' can be considered as synonyms too. The word 'long - winded' emphasizes that the story might be a bit tiresome because of its length, similar to how 'long' in 'it's a long story' gives the sense of it taking a while to tell. And 'yarn' is an informal way of referring to a story, so 'lengthy yarn' also means a story that is long.
It could be 'it's a protracted account'.
A long tale. For example, 'The Odyssey' by Homer is a long tale full of adventures.
A long tale. For example, when we talk about the legend of King Arthur, it is like a long tale filled with adventures, romances and heroic deeds.
Epic, saga, tale. These words can be used in place of 'long story' in many cases. For example, instead of saying 'Here is a long story', you could say 'Here is an epic' or 'Here is a saga'.
Some synonyms could be 'a lengthy tale' or 'an extended narrative'.
You can say 'He told an elaborate account of his adventures.'
A drawn - out story. For example, a long - winded fable that goes on and on with many details and moral lessons.
Narrative. A narrative can be a spoken or written account of connected events, just like a story. For instance, a historical narrative tells about events in the past in a story - like way. It often includes characters, a plot, and a setting.