Hello Ron,
The letter for the negative PCR is can be both in paper or electronic, as long as it comes from an official source (ej: a certified doctor, clinic, testing center, etc). Please bear in mind that the restrictions in Ireland are constantly changing, so the best place to stay up to date is the
traveller health page. You can keep on top of the current situation and recent changes by following helpful links to the governments’ guidelines there.
Have a fantastic day!
David