Sadly there is - as far as I know - no ‘list for dummies’ of how the Home Media section of the Horizon works.

What you mention are the file formatting methods of Apple respectively Microsoft.

The important thing however, is the codecs that is used for the files, that you want to playback via the Home Media player of the Horizon.
Usually you must format the stick as FAT32 (which is part of the Microsoft file formatting) ——— which (video/audio) codecs, the Horizon then can decode, is hit or miss!
I know of no list there - but you can find some information on the internet e.g. here:

Thanks again - wise words - sage advice. I will capture the results of some testing from yesterday:

1. memory sticks work; however my current inventory was of only small capacity units
2. so I bought new portable usb drives ... and then discovered the FAT32 limitation ... so I had to partition the drive to get the "right" size for FAT32 formatting to then get recognised by the Horizon's Android operating system ... not cost effective, and possibly difficult people to navigate across three to four logical drives on one physical drive ... so I abandoned the hard wired approach
3. therefore I resurrected my PLEX system from 10+ years ago, when I got our first BV (an 8-32) and I was using my 1st MacBook (later the 1st MacMini) as a media centre
4. amazingly on the Apple side it still worked (even without bringing the software) ...and the MacMini's PLEX server popped on the HomeMedia menu :)
5. I then upgrade the PLEX software (heart in mouth in case something broke ... it all worked fine)
6. the PLEX directory access leaves much to be desired (in my opinion) ... see the screenshots ... and whilst some files a playable, so were not (see list below)
7. at first (prior to writing this!) the big issue was the Horizon's access of the video portion times out after about 2 minutes ... however the audio keeps coming through ... I then found (while taking the attached screenshots) that the timeout happened on the builtin menus too!
8. so I dug around the Horizon's settings and found thetimeout (now adjusted) and the wake-up from WLAN (the lack of which (from the B&O iPhone App) had started to irritate me me)
9. so as of now we have a happy me and more importantly a happy wife

As an aside, most of the media on the PLEX system is either ripped from our DVD collection, or downloaded ... from memory the .flv format is from the era when I was downloading (YouTube?) content ... and is not playable of the Horizon. I seem to have misplaced some of my Plex music files from the Linn annual playlists (old forum members may recall be publishing those announcements and their legal download access areas) ... they are in the PLEX meta-data catalogue but not on the MacMini's HD nor the my archived HD ... from memory they are in ALAC format, and I hope that is supported once I find those files! The list of formats that do work are: .avi .m4a .m4v .mkv .mov .mp4 Over and out for now as I have a commercial project to completed ... so no B&O games for some weeks.

“9. so as of now we have a happy me and more importantly a happy wife”
?

If you find your ALAC files and they don’t play, converting these to FLAC should be an easy task.

MM

Thank you … still trying to find them!

their folder on various backup devices is empty !

did Linn mark them as “do not copy” … or give them expiry dates ?  And are those options even possibilities ?

truly strange