It is not HTC or Samsung, it is Android that changed. Once they adopted MTP to transfer files, I think MTP is a Microsoft proprietary protocol when devices are plugged to a computer.
There is a plug in for your file manager to allows you to connect your device though.
You can try. Check this link for how to
Or you can wait at the end of April the new Ubuntu LTS is going to be release and already comes with the plug in included in the OS.
Good luck to you