Hi!
According to some dictionary of Irish (all the words are written in Cló Gaelach there, though it was published in the middle of the XXth century, still don't remember the name) they pronounce the words like "neamhbheo" (with the lenited b and m coming after the prefix neamh-) as /n'am'o:/ in the South. Is it characteristic of South Irish only?
Thanks

In Munster Irish, sometimes a b has no séimhiú although it should have, after words ending in -m.

For example, I remember a poem by Máire Mhac an tSaoi, with this: "fém béal" (Standard: faoi mo bhéal). Normally there should be a séimhiú on b, but since it is a bilabial consonant, as m, there is no séimhiú. I think the same phenomenon (or quite) happens in your example of neamhbheo. I don’t think that exists outside Munster.