I usually get mine from either Bandcamp or Amazon. No DRM from either when downloading, though buying music from Amazon gets difficult if you have an Amazon music subscription.

Bandcamp allows to buy drm-free music. You can just have the files on your desktop and play them, or use an app like Jupii (available as a Flatpak) to play your Bandcamp library. I havnt tested the app myself yet tho.

I use Qobuz. They have options for high quality flac downloads. Their download app isn’t native Linux, but you can download one by one from the web.

Bandcamp and Qobuz