Offering my experience into the discussion for what it's worth, or who it might help. I downloaded the maps.zip file as described above, along with all the pdf manuals I could, which took about 45 minutes. I then unzipped (Windows 10) and did a copy to a blank quick format 64GB USB stick (format exFAT) which took about 3 hours. I simply copied the maps\ level folder to the root.
Then out to the car (MG ZS Long Range Trophy 23 Reg) and plugged in USB stick. Wait about 5 minutes for the system to read and identify the USB files - only the top box was selected to update maps. Click OK and sit back for about 45 minutes while it read and transferred the files. Offered reboot and now updated to 22Q2 from 21Q1
A few other things I had tried, but failed with were the wrong versions of the maps, using the USB C socket (this doesn't seem to work with anything) and various failed copies to other USB sticks.