I'm not referring to the music from the official games, obviously. Those are easy enough to find. I've been trying to find relatively updated forums/blogs where download links for this music is shared. I'll start dumping some of these blogs I find, and if you know any of them, feel free to share!

https://www.tapatalk.com/groups/bunbunmaru/musica-de-touhou-f13/index-s100.html (this type of forum is so nostalgic holy shit)

http://touhounosekai.blogspot.com/

https://moriyashrine.org/files/category/27-music/