Excuse my total ignorance, but how do you go about connecting your Mac, so that I can do the same.
On your mac, open SystemPreferences> Sharing make sure Internet Sharing is enabled.
In Finder click on Go in the menubar and select Go To Server.
Enter the IP address for your 5000T, in my case smb//:192.168.2.3
You should be able to see the IP address of the 5000T in System Preferences> Network> Ethernet
as long as you have set up the network on the 5000T
Freeview> Settings> Network Settings> Configure LAN
When you have the IP address of the 5000T in the Connect To Server field press Connect
the mac should after a short while offer you a dialogue with various options.
Click on Download press OK.
The mac should then Mount a Volume called Download on your Desktop.
Open that and you can drag and drop files onto that and they will be copied over to the 5000T
On the 5000T click Freeview button> Media.
Depending on the sort of Media you have dropped over to the 5000T select Video, Music or Photo
and as long as the type of media meets the protocols of the Humax you should be able to view or listen to
the files you have transferred.
Some experimentation may be required as the Humax manual for the 5000T does not go into great detail
or impart any great knowledge of which files it can or can't play. This is due to file types and various
video and audio codecs changing or being introduced, so you will learn on the hoof so to speak.
If you encounter any problems or need clarifying on details please write back and describe any problems
or questions in detail so that I may help resolve any problems.
It may help if you included which mac OS operating system you are using on your mac, for me my mac is
connected to my 5000T by Ethernet cable and running macOS Mojave 10.14.6.