We recently released the rustls-platform-verifier crate, and the rustls team believes this is probably the best option for most client use cases (especially on platforms like Windows, macOS, iOS and Android), since it reuses the platform verifier instead of more naively trying to find installed roots (which might be subject to additional constraints when used in the platform verifier).

This has been used for years inside the 1Password multi-platform client codebase, so it is more mature than it might seem at first glance.

I actually started adding support for this, but unfortunately it doesn't currently have great support for adding additional roots on some platforms, so the current form of feature additivity that reqwest uses (adding both webpki-roots and rustls-native-certs) doesn't work on some platforms (it only works on Linux, where it is needed the most because there is no real platform verifier).

I think this should probably become the default going forward.