> For most apps on non-mobile devices, there isn't filesystem isolation between apps.

If there isn't there should be. At least my Flatpaks are isolated from each other.

> Apple/Microsoft/Google all ship encrypted storage for secrets (Keychain, Credential Manager, etc), because restricting key material access within the OS has merit.

The Linux equivalents are suspicious and stuck in the past to say the least. Depending on them is extra tedious on top of the tediousness of any PGP keyrings, god forbid a combination of the two.

> Basically everything in PGP/GPG predates the existence of "corporate security circles".

Then we know where this stuff came from.

> Then we know where this stuff came from.

I can’t figure out what you mean by this.