I got my OnePlus 6 to sync.
You should not need to use developer settings. When you plug it in you will get a notification. Click on it and you select file transfer.
Then you go to tools > options > handheld and select either playlists or the entierty of your music library. You probably already did this part for your ipod.
In the action window at the left bottom you should be able to select handheld and hit sync.
The only thing I didnīt figure out how to sync the actual playlists. You can select playlists, but it does not do anything besides syncing the music in the playlist. I at least end up without an actual playlist.
Itīs deffinitely possible from a technical standpoint to sync playlists to android. Android does have system wide playlists that will show up in any music player that does not use itīs own thing. Also MusicBee could do it just fine.
EDIT: Under tools > options > handheld > files, paths, & more there is an option "Write Custom Playlist files". Iīm trying this right now, but itīs taking 23 minutes to sync. Deleted all my music again, because my phone said I have over 60gb of music, witch I donīt have that much music. Turns out es file explorer has a recycle bin option. So in 20 minutes I can tell you if that worked with phonograph. This however has nothing to do with androids system wide playlists. But Iīm hoping phonograph will pick up the m3u files as well.
EDIT2: It did pick up the m3u files as well. But your milage with this may very depending on what music player youīre using and if it can do that. Except, maybe android itself can read them and puts them into the playlist database. That would also be likely. But iīm just guessing at this point.
EDIT3: It seems to have some trouble with non-conventional names however.
https://imgur.com/a/D5Svb5DI have some electro swing playlist here and this entire album from caravan palace does not show up, because the album is called <|°_°|>
Iīm hoping the android app jriver supposedly has in the making gives us a better way so sync the library more conviniently without problems.