This is a very harrowing read: https://en.wikipedia.org/wiki/Executions_during_the_Irish_Civil_War

I haven't come across any songs about James Fisher, Peter Cassidy, Richard Twohig and John Gaffney who were executed at Kilmainam Gaol in Nov 1924 for possession of revolvers.
https://www.rte.ie/news/2022/1112/1333890-take-them-out-and-shoot-them-irish-state-executions/

This week marks the centenary of the "Drumboe Martyrs", four men executed by the Irish Free State government on 14 March 1923, they had been found guilty months early of arms offences, but the decision to execution them was only made as a response to the killing (by other members of the anti-treaty forces) of a national army soldier. Lyrics of three songs about the Drumboe executions are now published in the Mudcat thread Woods of Drumboe

Bob Feldman composed a song about Liam Mellows Bob Feldman https://www.youtube.com/watch?v=essfjedOExo
and Teresa Brayton, who wrote the lyrics of the popular song "The Old Bog Road", wrote a poem "Liam Mellows" https://www.poetryascommemoration.ie/poems/liam-mellows-by-teresa-brayton/. She doesn't mention Mellows' socialism, which was key for Feldman. I haven't looked at all the poems posted at https://www.poetryascommemoration.ie/virtual-poetry-wall/, but I see it includes poems about the Civil War in Ireland.

Lovely Annaghdown is a song about Máirtín Moylan, one of the Tuam martyrs https://annaghdownheritage.ie/mairtin-moylan/

Mai King O'Brien wrote a poem about the Tuam Martyrs called "The Six"
https://www.oughterardheritage.org/content/people/seamus-o-maille/the-six

Niall Teague's song "Dutiful Son" is based on the last letter of another of the Tuam Martyrs, Frank Cunnane, to his mother
https://www.youtube.com/watch?v=9JRH-o8oJIw
(the other lyrics mentioned are currently available on line, although not yet added to Mudcat; can anyone transcribe 'Dutiful Son', or otherwise obtain the lyrics for us?) The actual letter is transcribed at https://www.oughterardheritage.org/content/people/seamus-o-maille/last-letter-of-frank-cunnane