streamlocal extension

[Vampire]

A row for the streamlocal extension with which you can forward from and to unix domain sockets (from and to unix domain sockets or tcp ports) would be nice.

[fingolfin]

You mean add this on https://ssh-comparison.quendi.de/comparison/extension.html ?

If anybody is interested in working on this, I suggest these steps:

1. figure out the relevant RFC
2. add it to https://github.com/fingolfin/ssh-comparison/blob/gh-pages/_data/specs.yml and make sure to add a protocols: extension: section, similar as was done for RFC 8308
3. now the hard part begin: go through all (or as many as possible) of the implementation files and add streamlocal to the supported extensions (if it is) (for an example how this was done for other extensions, such as server-sig-algs , see https://raw.githubusercontent.com/fingolfin/ssh-comparison/gh-pages/_impls/bitvise.md)

[Vampire]

You mean add this on https://ssh-comparison.quendi.de/comparison/extension.html ?

Exactly

figure out the relevant RFC

I'm not sure it is an official RFC.
It is an OpenSSH extension.
You can find its technical description at point 2.4 ("connection: Unix domain socket forwarding") of https://github.com/openssh/openssh-portable/blob/master/PROTOCOL.