> There are essentially no mainstream systems that don't [use PQC/ECC hybrid cryptosystems?].
If so, good. I'll admit my expectations are a bit biased from having to deal with projects that go out of their way to produce defective software (eg DRM, malicious abuse of undefined behaviour by compliers, cloudflare and other captcha-walls, etc) so I tend to assume the worst by default.
Yes. So far as I know, there's no mainstream system that has even proposed to use solely Kyber and not Kyber+ECC. It's been a built-in assumption since the earliest Chrome PQC experiments.
> There are essentially no mainstream systems that don't [use PQC/ECC hybrid cryptosystems?].
If so, good. I'll admit my expectations are a bit biased from having to deal with projects that go out of their way to produce defective software (eg DRM, malicious abuse of undefined behaviour by compliers, cloudflare and other captcha-walls, etc) so I tend to assume the worst by default.