The web version of spotify doesn't work on my m2 air in either chromium or firefox. The Spotify website errors with: "Playback of protected content is not enabled."

Slack works just fine from the browser on Asahi though.

You're likely missing the Widevine DRM plugin. IIRC, many distros don't include it, or don't enable it by default.

Where is the publicly available linux/aarch64 build of widevine drm?

The fetch-latest-widevine.sh[0] script says 'Architecture not supported'.

[0]: https://github.com/proprietary/chromium-widevine/blob/master...

Well, to answer this question if someone comes looking: there's no official aarch64 widevine release, but chromeos just started shipping a 64bit arm version of widevine in the last month. But that version is incompatible with the 16k page size kernel that asahi ships with. There was a report in the asahi irc channel that a manually patched libwidevinecdm.so works.