Northern Irish accent where “mother” is pronounced “muller”?

I've been listening to the podcast Decodong the Gurus and one of the hosts is from Northern Ireland. He seems to have an Northern Irish accent I've not heard before. He pronounces the word "other" like "uller", "mother" like "muller" and the name "Heather" like "Heller". Is this from a specific region of Northern Ireland? I feel like its distinct from what I've heard before, although I can't claim to be too familiar with Northern Irish accents

Thanks!

Edit: here is an interview with him here at around 2:50-something-ish he says "rather" and it sounds like "ruller" to me