It's definitely similar to "Londonderry Air" in some spots, but it's not the same. As far as my original question goes, I should learn to read video descriptions as the one for that video specifically says who originally recorded it...
I can often spot missed covers of less well known songs (e.g. deep cuts) with which I'm familiar but generally do not have the editor's ear for spotting derivative works. This means that if I can hear work ABC in work/performance XYZ, then something's probably there.
I listened again and, while there's some material but not heavy rearrangement, I still hear gold ole "Danny Boy" in there.