They are what are called 'skins'. In this case they are skins on the Cake network. Cake looks the same. Think of this particular situation like a big round building, with poker tables inside and many doors. Different companies run each door. They make money via the rake at the same tables you might play by coming through any other door into that same poker room.
There is at least one other site with a Cake skin, but the name escapes me at the moment. The support may differ among skins. SOme support is actual game related and each site will forward those inquiries to whoever is running the engine. Other inquiries are not game related, but maybe money related and each site would handle those separately.
Among other skins would be Absolute/Vegas247. How this works is not real clear.
There are other networks with skins.
More info here
https://www.cardschat.com/forum/general-poker-13/all-about-skins-100550/?highlight=skins