@aral does macOS force-retheme third party app icons? No! What they do is design a consistent set of icons for their apps, and provide clear guidelines for third-party designers to design their own.
That's exactly what upstream GNOME folks are doing now. Pop!_OS should embrace that.
If you don't like a particular icon in an app that hasn't been updated, nudge the developer to redo the icon with the guidelines in mind. Same as you would if you don't like an icon of a macOS app.
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