With Unikraft as being a librarized unikernel system you can actually choose if the OS layer should provide you a network stack (likely written in C/C++) for your runtime or if you prefer doing it in a higher-level language. Similar to this the MirageOS folks developed a network stack in OCaml.
This is true, there are a number of embedded frameworks that you could use as well and even run it as virtual machine too. In contrast to this we want to make it as seamless as possible by still providing you the Linux-OS-like layers if you need them. The goal is that a previously developed app for Linux should be seamless to port. The OS interfaces in the higher-level language should be the same as you have it on Linux, so no code changes.
