Indeed. Taillte Ireland's (Ordnance Survey Ireland's) detailed cartographic data is also not open (including historic data - maps from the 1820s and 1920s!) and it's really a huge pain in the ass. On the other hand, OSM is in pretty good shape at least for topographic information. I've used it to make hiking maps here and nobody's died - as far as I know.

As a side note, I was one of the initial developers of the Irish national open data portal. Earlier today I had Claude look for similar LIDAR data for Ireland and I saw it pull from the site I built a dozen years ago and I was unreasonably pleased with myself :)

I’ll add the UKHO Admiralty marine charts to this list too.