Edit: It looks like i'm wrong DVDFab does not support UHD ripping as it has not been cracked yet.
it does say "HEVC Decoder" support. the manual will tell you more information like which containers are supported. aka MP4, MKV, etc. For the harddrive I dont see why it wouldn't support a hard drive if its formatted correctly. Like my Vizo Tv only supports FAT32 format so any file over 4gb won't show up. Once again the manual might give some insight on the flash drive formatting (which is the same for an external).
I cannot find the manual on the site....