Another source are good ol' CDs. If you know where to look you can get them cheap too. Specialist charity shops that specialise in records and CDs in student or wealthy areas are good, as are second hand stores online.
An alternative to self hosting is to use an online music locker. I wrote up a bunch here: https://www.blisshq.com/music-library-management-blog/2021/0... and (disclaimer) operate one myself: https://asti.ga