Well, 1921 was the Second Dail. The First Dail was 1919.

There were, in effect, four factions in the 1921 Southern elections. Sinn Fein, who wanted to secede. The Dominion League, who wanted independence on terms similar to Canada: self-government within the Commonwealth. The Anti-Partition League, which wanted Ireland to remain some part of Great Britain. And the Independent Unionists, who wanted Ireland to remain part of Great Britain and opposed devolution in general. The other three were organized parties, the Independent Unionists were a loose collection of mostly independent politicians.

Sinn Fein won every seat except for the University of Dublin, which returned four Independent Unionists: Ernest Alton, James Craig, Gerald Fitzgibbon, and William Thrift. Every seat in the election was unopposed: Sinn Fein didn't put up competitors for the Dublin seats.

The four men were elected in May and met once on June 28th 1921 to discuss the upcoming Dail and their positions. While the exact comments of the meeting were not, as far as I know, recorded, they all agreed that the Dail was opposed to their beliefs and to refuse to attend. They believed that the British government adequately represented their interests and felt obliged to side against the ongoing violence. They all refused to attend. Instead, they returned home and went back to their (mostly academic) jobs. One went back to being a professor of mathematics, for example.

So, what were they doing? Maybe grading undergraduate papers. Whatever it was, it wasn't politically notable.

They would be more active in the next Dail, all four winning their elections again. But that was after the British government had made peace overtures to the Irish and no longer opposed the existence of the Dail.