Pretty cool! Adding kTLS is definitely an improvement. I made an actually zero-syscall per request server a few years ago (and blogged about it at https://wjwh.eu/posts/2021-10-01-no-syscall-server-iouring.h...) but as TFA notes it comes at a heavy cost of constantly busy-looping.

io_uring is very cool tech though and has been progressing at an impressive pace the last few years.