Take a look yourself.

Our code is as good as we can make it, and everything is modular and well documented. For example our QUIC implementation noq which underlies every iroh connection can also be used as a standalone QUIC impl that implements QUIC multipath.

https://docs.rs/noq/latest/noq/

If we wanted to have "total bespoke and unusable code" we would have inlined all of this into the iroh repo to make it unusable.