Mopidy MusicBox VS mpd

Is there a reason you need to use carplay instead of something like pi musicbox? What exactly is the USB dongle for?

I saw something here on reddit where people were taking the little $5 raspberry pi zero's and basically building their own chromecast audios with them. I am not sure this is the same thing I saw but I found this on google. https://www.pimusicbox.com/

I have a few rooms in my house which I have audio, but they are far enough apart that I won't be trying to stream to all at once. I am also a mostly Apple user, so I use Raspberry Pi's with Hifiberry AMP2 and shairport-sync (AirPlay target). I can select any of the Pi's as the speaker output on any Apple device. There's also a pre-made Raspberry Pi distribution called pi music box which also offers other protocols than AirPlay.

Get yourself a Raspberry Pi and battery pack if you're mobile, and check this guide out. That'll run Spotify 24x7.

Look what I've found: https://www.pimusicbox.com/ This should perfectly suit your needs..

Currently, my plan is to use https://www.pimusicbox.com/ with some sort of DAC, an undetermined raspberry pi model, and a micro SD card for storage (total flac library is just under 500 gigs). I'm not incredibly well versed in pi projects (have made a few successful retropie builds for friends) and am an amateur when it comes to coding and linux. Regardless, this project will be a hobby , so learning, failing, and growing are all part of the plan.

Pi MusicBox

https://www.pimusicbox.com/ I found this which has chromecast support and airplay, but it doesn't support rpi4 it seems

Last week I released v1.0.0 of MphpD - a fully-featured, dependency-free PHP library for the Music Player Daemon. It's my first take on a library so feedback and suggestions is very much welcome and appreciated.

mpd server + mpd clients? https://www.musicpd.org/

Eventually I'd like to continue with the other frontends I have planned, starting with festivald which will be a music daemon, similar to mpd.

It's not written in Java, but if you want to look at some source code and/or protocols to see how it's already been done, look at mpd (https://www.musicpd.org/). IIRC, it actually uses TCP.

Well, it’s a slightly odd use case in that normally the server would just be the server and not also the player, but given the kit you’ve got it makes sense. Probably what you want is MPD plus one of the MPD web clients.

You want SnapCast. You'd run snapserver on your Linux box and snapclient on your Pi's. Snapserver has support for Airplay (via shairport-sync) and Spotify (via librespot). I recommend using MPD for your music library, as I don't think PlexAmp can output audio in a way that's useful for snapserver.

If it is just music, have you considered MPD or similar? An entire DE seems like overkill. There are several good options for doing this and they're not difficult to set up. Even good ol' VLC has an HTTP interface option so you can set it to allow connections from your LAN, then launch in that headless mode, inside tmux or as a service, limited to files from a specific directory tree. It's then controllable from any device on your LAN has a web browser.