Add https://adamws.github.io/kicad-kbplacer/repository.json to KiCad's repository list to use these packages:

{
    "packages": [
        {
            "$schema": "https://go.kicad.org/pcm/schemas/v1",
            "name": "Keyboard footprints placer",
            "description": "Plugin for mechanical keyboard design",
            "description_full": "Plugin for mechanical keyboard design.\nIt features automatic key placement and routing based on various layout descriptions like kle-ng, ergogen and via.\nTo learn more visit project's homepage.",
            "identifier": "com.github.adamws.kicad-kbplacer",
            "type": "plugin",
            "author": {
                "name": "adamws",
                "contact": {
                    "web": "https://adamws.github.io"
                }
            },
            "license": "GPL-3.0",
            "resources": {
                "Homepage": "https://github.com/adamws/kicad-kbplacer",
                "Bug Tracker": "https://github.com/adamws/kicad-kbplacer/issues",
                "Sponsor": "https://ko-fi.com/adamws"
            },
            "tags": [
                "keyboard"
            ],
            "versions": [
                {
                    "version": "0.15",
                    "status": "development",
                    "kicad_version": "6.0",
                    "download_sha256": "1f14e74b3888cc7412a404fb6900512351c0d6c84b141f549c44b4a5332cc9d3",
                    "download_size": 285306,
                    "install_size": 280296,
                    "download_url": "https://adamws.github.io/kicad-kbplacer/kbplacer-0.15.dev45+g0de34061d.zip"
                }
            ]
        }
    ]
}