Reported on the community forums:

In artist pages in Musicbrainz the bootleg and promotion release groups are hidden by default. But in Listenbrainz bootleg and promotion releases appear together with the official releases. i suggest hiding like on Musicbrainz, or separate them, like with Remix and Live releases, which appear at the bottom.

This is visible for example on Mariah Carrey's page: "My Shooting Star" and "There Goes My Heart" are bootlegs (see attached screenshot).

Currently in LB artist pages we get a list of Release Groups, which will not have this "bootleg" status as those are applied at the Release level instead. Not sure how we can detect those bootleg releases.

For completion, here is the data we currently have available for one of the examples pointed out:

{
    "json": {
        "artist_credit_name": "Mariah Carey",
        "artists": [
            {
                "artist_credit_name": "Mariah Carey",
                "artist_mbid": "494e8d09-f85b-4543-892f-a5096aed1cd4",
                "join_phrase": ""
            }
        ],
        "caa_id": 27383806932,
        "caa_release_mbid": "40cc8400-e412-4905-8c8a-40900980bc00",
        "date": "2009",
        "mbid": "c16e7294-41b5-415c-a550-9bcf82493e27",
        "name": "There Goes My Heart",
        "secondary_types": [
            "Compilation"
        ],
        "total_listen_count": 714,
        "total_user_count": 133,
        "type": "Album"
    }
}