File explorer for Windows and Android

Hey. I'm looking for a file explorer/picker dialog that would work for Windows and most importantly for Android (it doesn't have to be the same file explorer). I've found a lot of questions about this matter and most answers lead to paid custom assets from the store that I can't afford (like UniFileBrowser), so it must be free.

The files that the user has to pick and load are music files so the Android photo gallery browser feature isn't an option.

If there are no assets/libraries/native libraries I could use, I'd really appreciate any advice on how to create my own file picker, since I have no experience in this. I'm especially concerned about Android and accessing external memory.