I know it's churlish to complain since Irish duolingo is a wonderful thing and I'm grateful for all the work that's gone into it and it's something that will improve with use, but:
I wish it wouldn't be so hard on Hiberno-English, it rejects "I amn't" for "I'm not" and "guards" for "police" and "be buying" type constructions in the verbal noun section and even, once, "That's a different story altogether" though thankfully that's been fixed.
I would always use ye for sibh. I would never use you for sibh. Not sure about y'all though is that the american y'all?
Southern English and African American English both use y'all, whereas other American dialects use "You guys". I speak pretty much standard American English, but I use y'all (and some other features of Southern English) because my mother used to live in the South. Also, the fact that English doesn't have a universal pronoun for the 2nd person plural kinda bugs me, since most other languages do. If we don't have a "y'all" (or a "ye", in your case), what's the point in having a "we" or a "they"?
I think you have a point about guard, but would you expect them to accept 'ain't', because it's the same thing? There's a difference between accepting feature of standard Hiberno-English that would be used in normal interactions with people you don't know, or in an email to your boss, and accepting slang that is a feature of spoken rather than written English.
Don't mind me, I'm only giving out because it caught me off guard by rejecting "I amn't", which is how I speak and, when trying to translate Irish, it's hard to remember to write more formally, more proper Englishy.
It wont accept ye as in what are ye up to. It drives me cracked. Otherwise i love it
But not the Hiberno-English - it'd seem reasonable for the Irish course to accept Hiberno-English, it often gives the more natural translation! Also, sibh is youse.