I see. The court system is pretty much as I suggested. Tell the relevant Minister to extend that methodology to all situations where an oath is legally required and we're sorted.
https://www.decisis.ie/legal-news/oaths/By: Mark Tottenham BL, on March 8, 2019
Before giving evidence in an Irish court, most witnesses are required to swear an oath to the following effect:
“I swear by Almighty God that the evidence I shall give shall be the truth, the whole truth and nothing but the truth.”
The requirement to make the oath in this form arises under the Oaths Act 1909, which sets out the prescribed forms of oaths for Christians and Jews. This is that Christians should hold the New Testament, and Jews should hold the Old Testament when making the oath. The Act preserves the right for a person who is not Christian or Jewish to take an oath in any manner then lawful.
If a witness objects to being sworn on the grounds that he or she has no religious belief, or that the taking of the oath is contrary to his religious belief, he or she is permitted to make a ‘solemn affirmation’ instead, under the Oaths Act 1888.
The legislation has not been updated since independence in the 1920s, nor since the introduction of the constitution in 1937.