Most of the good ones have been called out, but to add to some more info:
Acoustic Sounds - usually have a discount code available for downloads, between 10 and 15%, they are also a great resource for vinyl if you are into that.
HDTracks - create an account and sign up for offers, they run 15-25% off codes with regularity
Bandcamp - a good source for lesser known, indie and occasional big names (Peter Gabriel sells there now). Can stream and download in a variety of formats, often include "name your price" and a higher percentage of sales go to the bands/artists than many sales pipelines.
7 digital - not bought much here but they do have some offerings the others lack
Rip CD's - Use market has seen a bit of an uptick during the pandemic but still a good option for obtaining lossless files... and you have a backup should you ever experience a corruption issue.