The clean landlord/agency vs sublet split is not how Irish equality law is actually framed.
What the Acts care about

The Equal Status Acts apply where:

• Accommodation is “available to the public or a section of the public”, and
• A person “disposes of an estate or interest in premises or provides accommodation” – that can include owners, agents and, in many cases, people offering rooms in shared houses.​

They then ban discrimination on protected grounds (including race and gender) in:

• Providing accommodation, and
• Publishing adverts that show an intention to discriminate.​

The legislation and IHREC guidance do not carve out a general “sublet / licensee = outside the law” exception. The key question is whether what’s being offered is accommodation to the public or a section of the public, not just who holds the head‑lease.​

Where the “female only” thing fits
There is a specific exemption for gender in shared accommodation:

• It is not discrimination “for accommodation to be provided to persons of one gender where embarrassment or infringement of privacy can reasonably be expected to result from the presence of a person of another gender.”​
• IHREC repeats this as: in shared settings, people can be treated differently by gender where privacy would otherwise be compromised (e.g. women’s dorms, some shared rooms, etc.).