I'm asking this question here because I've had some difficulty finding the answer through normal internet searches (through Google, DuckDuckGo, etc).

I'm currently a student of Byzantine chant, and have dabbled some in Western Church chanting styles as well (Old Roman, Gregorian, Templar Chant, etc). One thing I like about these is since they're based on modes, the music fits to the lyrics instead of the other way around of trying to force the lyrics to the music. When I hear Sean Nos, it also sounds modal to me, and being drawn to this sort of music, I'd like to learn more about it.

TL;DR; The actual question:

All I could find about the rules in my searching is that it utilizes 4 Western modes (Ionian, Dorian, Mixolydian, and Aeolian) and that pentatonic and hexatonic scales are used, but I'm wondering if Sean Nos could be categorized similarly to the old Gregorian style as having 8 modes, 4 authentic and 4 plagal which begin a 4th below their corresponding authentics?

The reason I ask this is if it does bear these similarities, it may be appropriate for use in liturgical hymns, and I've taken an interest long-term in composing such music. For instance, I thought Caitriona O'Leary's rendition of Donal Og sounded like a style that could fit well with some hymns sung for Holy Thursday and Holy Friday services of Passion Week. If Sean Nos could fit into an 8-mode system, I'd probably take on the effort to learn the rules and try to compose a few hymns.