In 2020 the openstreetmap community in Ireland are invited to work on a campaign called #osmIRL_buildings. The name reveals that it is an effort to add as many of the buildings on the island on to the osm database. A future launch of this project will take place, so for the moment the beta phase is to explore how we get on with the task in a few select counties, and what sort of guidance is needed to accurately capture these features.
There are almost or approaching 5 million buildings on the island, though this is an estimated total garnered from official sources for both jurisdictions. The osm databases currently has 900,000 buildings.
To participate in the beta phase please look at the tasks here, and please join the group Telegram chat used by the first 30+ contributors to give feedback, chat, and asks questions.