Nowadays there are many niche conferences in different subareas of ML. However, I think it will take some time for those niche conferences to be "mainstream" in the specific subarea, because prestige matters (especially in job application) and those niche conferences are just not as prestigious as the top ML conferences, at least for now. See here for a discussion: https://www.reddit.com/r/MachineLearning/comments/vjqdom/d_niche_ml_venues_vs_top_ml_conferences/?utm_source=share&utm_medium=web2x&context=3