Well, I'm afraid that I'm not able to read #gaeilge yet but qualifying books:
@nichorra wrote Elysium, set in Cork. #LGBTQ
Fierce New World is a short story compilation by Irish writers.
@spongepaddy wrote Hollow Oaks which is a modern fantasy (CW for violence in parts) but very readable and #trans friendly
I haven't worked my way through "Space Navigator and other stories" yet but I believe that is Scifi.
@TabletopScot might be able to suggest Celtic SFF authors.