Would it be an option to use io-uring to further recuce syscall overhead? Perhaps there's also a way to do zerocopy?
When Josh et al tried it, they hit some fun kernel bugs on certain kernel versions and that soured them on it for a bit, knowing it wouldn't be as widely usable as we'd hoped based on what kernels were in common use at the time. It's almost certainly better nowadays.
Hopefully the Go runtime starts doing it instead: https://github.com/golang/go/issues/31908
Besides kernel supplied offloads, the thing which helps further is actually bypassing the kernel with AF_XDP or DPDK. But those techniques will have other challenges and limitations.