There's this one, but it only seems to have 3 members: 🤣
https://celticthunderfans.proboards.com/During the early years of Celtic Woman, social media wasn't nearly as widely used as it is now. Forums were the main way that fans from different places interacted. Celtic Thunder started around 4 years after Celtic Woman. During that time social media grew quite a bit. There may have been less dependence on forums for news and fan interactions by then, although the old Celtic Woman Forum was still pretty active for several years afterwards.
Celtic Thunder also has a different approach to fan engagement, including social media, StageIt shows, etc. Fans seem to network with each other more directly or on social media, rather than through a Forum.