I’m using the Mercator domain mapping plugin https://github.com/humanmade/Mercator but Hummingbird isn’t working fine with this plugin.
When I have it enabled, my mapped subsites won’t load the Hummingbird CDN. Also it is having some random situation, on the wp-content/hb-cache/. Sometimes it does not create the cached file for mapped domains, when it creates, I can see it creates two folders, one for mapped domain and another for default subsite URL, if I try to flush the caches it is only removing the default WordPress URL, the mapped domain caching keeps.
When I try the default WordPress mapping, it will works correctly.