There is an increasing amount of research into Ulster's Irish speaking Protestant community. Dr Peter Toner Sr's well known research into the predominately Presbyterian Gaeltachtaí (Irish speaking areas) in New Brunswick, Canada, in the mid 18th Century well into the 20th Century, made many aware of this largely understudied aspect of Ulster history.
Many Irish speaking Ulster Scots descend from the migration of Argyll and Hebridean Redshanks into Ulster in both the 1500s and 1600s. Recently as Irish census records of the early 1900s have come on line some Ulster Presbyterians have discovered Irish speaking ancestors. As these Ulster Scots migrated to the New World, they often brought their Gaelic language with them.
Below, a link to The Irish Times article Ulster says Tá, which highlights the growing interest in learning Gaelic among the Protestant community in east Belfast.
Link: Irish Language in East Belfast