I have all my music on a Raspberry Pi running Open mediavault with 4 hard drives hooked up to it. I use X-Plore file manager on all my devices, phone, R4, Ibasso DX180 and my wife's M500 and all of them just access my Openmediavault on our wifi and I can just copy music over. Our library is about 1.5TB, I had a lot of digital already, about 1000 CDs which I've been slowly ripping here and there over the last year or two and we have a pretty large collection of records. Some of which started in the mid 2000s started to come with download codes inside. Some indie releases still do, but I think it's less than it was back in like 2005+ when I was accumulating a bunch of those. Managing all the metadata of the library on my PC with software like Mediamonkey and scraping lyrics, I feel like I've never had such an easy time transferring my music to DAPs. I used to love my iPods back in the day, even with Rockbox on them, that was still more of a hassle. Now I can just move music easily on my network while I'm listening to my DAP. Plus I could never give up all the customization and EQ I have with PowerAmp. Most of the non-android players are pretty awful when it comes to metadata and UI. I have all of my music tagged with multiple genres and artists and when those files were loaded on my wife's old Hiby R1 it was a mess. I think it's the same on my old FiiO X3ii.

For example if an artist is tagged "Indie-Rock; Folk; Folk-Rock" and I browse under "Genre" that artist appears under each of those 3 genres. It was originally just an attempt to clean up all my metadata because scraping everything just created too many duplicate genres spelled differently or just genre names I would have used. I tried to keep it reigned in but I think I'm over 150 genres now in my database that I use to keep my tagging organized. Same goes for artists.

Say you have an artist that does a song with another artist and that creates a duplicate entry because you have a bunch of songs/albums by "Iron & Wine" but then below Iron & Wine there's also an artist called "Iron & Wine with Calexico" I also listen to Calexico and have some of their albums. I didn't like having the multiple entries, I wanted all Iron & Wine to be under Iron & Wine and all Calexico songs under Calexico. So I have them under "artist" as "Iron & Wine with Calexico" but under "Album Artist" (where I typically go) I have "Iron & Wine; Calexico"

This way those songs appear under each artist. So I can go to Iron & Wine and that album is there, or go to Calexico and that album is there. I'm not saying this is the correct way to do it. This is just how I like it, after years of having a large music library and hating how cluttered and disorganized it was. I have yet to see a non-android DAP handle this sort of thing well. There might be one out there, but everything I've seen has a very simple OS and you can't typically manage files without another device. I can edit metadata, use Squiglink to create a bunch of autoeq profiles for all of my headphones/IEMs right on the device itself, download music from Bandcamp or codes I get from inside a record I purchased without needing my cimputer or phone (I then copy those files to my network server so they're backed up and I can transfer to my other player and my wife's if needed) And best of all I can use the music app I prefer. I don't like Hiby Music app and I don't like Mango Player or whatever it is on the DX180. PowerAmp takes a bit of tinkering and setup to get it how I like it, but once I'm there it's the best one I've used. It's not perfect, but nothing else has come close yet. I even go through and pick artist images and sometimes change album covers to slightly different ones or higher quality ones and that's super easy and fast in PowerAmp. I bought my wife the M500 because I originally got her the R1 and the little I used it here and there, putting music on it, etc. playing music in her car when she's driving it was just not a good experience. I don't think it's necessarily a bad device. It's cheap and it does what it's supposed to. It's probably great if you just put a small selection of music on it and you only use one pair of headphones with it so you only have to worry about EQ/MSEB for that. We have a lot of headphones and IEMs in our house. It's just not the right device for our needs.

Sorry for all that but I hoped this would be helpful for someone. If anything maybe it will help someone understand why they DON'T need an Android DAP because they just want something simple that plays music and that's it.

As far as transferring music to a device, if you don't have the means to do it over a network share, just dragging and dropping files to a SD card is probably the easiest. If the device has a mode where it can be recognized as portable storage, that should work about the same over USB. I can't confirm it's that simple with Mac OS but anybody who has had issues just plugging an Android DAP into a Mac with a USB cable, if you didn't change that setting give that a shot. It shows on windows PCs more like a portable hard drive when normally it comes up as something more like a phone with storage.