Im not gonna say i think im right or anything, or even that this is my only speculation, but
I think this season might be
Possibly set in london, not ireland
Set in early 1900s or late 1800s
Set during the Irish war for independance
Characters are either changelings or fighting changelings or kidnapped and replaced by changelings. Idk something about changelings
Could possibly be a system based off of or using Changeling: The Dreaming (possibly specifically an altered toys will be toys or something) OR Changeling: The Lost.
The poem in the trailer is "The Stolen Child" by William Butler Yeats. He wrote irish fairy tales and folklore. He ordered the poems and put the stolen child with other changeling poems and stories. The poem is about luring children away to escape the suffering of the world, but also leaving the good things.
The names are also interesting
Wyon is a prominent family who lived in England and irland up until the early/mid 1900s
Constance; Constance and even Con were popular names during this time in London/UK. Constance Markievicz was also a key player in gaining independence for the people of Ireland
Tiddlywinks is a game that came from victorian england, "it became one of the most popular crazes during the 1890s," the word tiddlywinks was derived from british slang. Tiddly was slang for alcohol. Tiddlywink has also been used as a name for faires in media before. And the tiddlywinks game boxes are sometimes depicted with fairies on the box playing the game.
Calypso has musical ties to french medieval music. It also means hidden or hider. Derived from the Greek Kalyptein meaning to conceal. It also has musical ties to trinidad and tobago, where the name may have derived from carrousseaux, meaning a drinking party/festivity - which is typical fae imagery.
Clyde is a name of celtic origin -scotland and northern ireland in reference to the river Clyde
Avery derives of Ælfred the literal translation of which is elf counsel.
(Im aware its Con stance, Tiddly Winks, and caly pso)