I have been using OH2 for a few years now and changing over to OH3.
Whilst creating my model, I have been using Semantic class’s for grouping(?) but I find that for me there are a few that are missing e.g. Gym or Workshop etc.
In the mean time you can tag it with a generic “room” and name it Gym. Honestly, I don’t really see the benefit of defining each and every room type that might exist in any type of building OH might be run in. Maybe there is something coming down the way that makes a difference but for now there is no functional or practical difference when tagging an Item as a kitchen compared to a bedroom or a bathroom.