tide-rustls 0.3 switches to async-rustls as the interface to rustls. tide-rustls is already rustls-specific, and using a rustls-specific async layer allows tide-rustls to expose more rustls specifics where needed.
tide-rustls 0.3 provides a new interface for custom TLS acceptors. A custom TLS acceptor gives you full control over the TLS negotiation process, and allows you to process some TLS connections internally without passing them through to tide, such as for multiplexing or custom ALPN negotiation. The upcoming tide-acme crate will build on this to provide automatic certificate management via ACME tls-alpn-01 challenges.