I waver on to what extent age is a protected category but normally err on the side of not caring about age-specific community arrangements to the extent that these overlap with pointlessness or have equivalents for multiple age groups. (E.g. a nursing home is not obliged to have children's classes if they have adult classes, because that would be silly, and a driving school does not need to admit twelve-year-olds, because for reasons that are not the school's responsibility twelve-year-olds may not drive).

Disability status (sensory, mental, physical, and to a lesser extent disease/addiction related) is protected but interacts strongly with pointlessness. Disease/addiction are less protected to the point where one might exclude alcoholics from a wine tasting on that characteristic alone, or send a kid home from school because ey has a contagious disease which is incidentally causing a temporary disability.

Nationality is weakly protected but interacts (through geographic location and language/culture) with pointlessness and with non-protected features, so tends not to look protected in terms of my reaction to various items.

If I had to describe a rule, I'd describe it in terms of the voluntariness of the feature, the background likelihood that people discriminate against those with this feature (not just the individual likelihood that the community-former is being exclusive for discriminatory reasons), and the difficulty/intrusiveness of hiding the feature should one want to do so. So, for example, race is maximally protected, because it's completely involuntary, racism is totally a thing humans do, and it's difficult to conceal.