With the above workspace setup/package configurations, the change in npm/cli#8431 specifically breaks installation of the platform-specific packages for lightningcss.
The lightningcss-darwin-arm64 et. al dependencies are all being flagged as "optional peer" dependencies, despite technically only being "optional" through the lightningcss dep. (verified via npm why lightningcss-darwin-arm64). What's interesting, though, is that lightningcss itself is correctly being flagged as a "dev" dependency (not optional, not peer).
The only fix I've been able to find for this is either installing lightningcss in the root package.json, or installing lightningcss as a dependency of services/b, even though it's unused.