Thanks for your input. Maybe the client ships in a way where it is compiled to only support MACs of 
hmac-sha1-etm@openssh.com,hmac-sha1

When I add these to my server I can SSH to it and see remote screen with X2GO client. If I change the server's SSHD config and remove the 2 sha1 MACs I can still shh to the server but X2Go client stops working. To get the libssh updated for my OS won't necissarily allow the client to use it if the client was statically compiled using an older version.

On Mon, 18 Feb 2019 at 12:22, Antenore <antenore@simbiosi.org> wrote:
Package: client

Hi Daniel,

I'm just a reader, but X2GO uses libssh, that support the Kex you are
using, so first of all, you have to install an updated version of libssh
and eventually check if it has been compiled with the support of these
algorithms.

Normally, I think, on the X2GO side there is nothing more to do.

Have a look here:

https://www.libssh.org/features/

On 18 February 2019 10:07:37 CET, Danie de Jager <danie.dejager@striata.com> wrote:
>Package: client
>
>The client does not support chacha20 as I get this error when I try to
>connect to the X2Go server. I did harden my SSH configuration as guided
>by
>Mozzila
>https://infosec.mozilla.org/guidelines/openssh
>
>When I use defaults it works fine. It seems that the library used by
>X2Go
>is missing some newer methods.
>
>Config:
>server ssh config:
>KexAlgorithms curve25519-sha256@libssh.org
>,ecdh-sha2-nistp521,ecdh-sha2-nistp384,ecdh-sha2-nistp256,diffie-hellman-group-exchange-sha256
>Ciphers chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,
>aes128-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-ctr
>MACs hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com,
>umac-128-etm@openssh.com,hmac-sha2-512,hmac-sha2-256,umac-128@openssh.com
>
>Client sshd config:
>Client using default sshd config
>
>or
>
>HashKnownHosts yes
>HostKeyAlgorithms ssh-ed25519-cert-v01@openssh.com,
>ssh-rsa-cert-v01@openssh.com,ssh-ed25519,ssh-rsa,
>ecdsa-sha2-nistp521-cert-v01@openssh.com,
>ecdsa-sha2-nistp384-cert-v01@openssh.com,
>ecdsa-sha2-nistp256-cert-v01@openssh.com
>,ecdsa-sha2-nistp521,ecdsa-sha2-nistp384,ecdsa-sha2-nistp256
>KexAlgorithms curve25519-sha256@libssh.org
>,ecdh-sha2-nistp521,ecdh-sha2-nistp384,ecdh-sha2-nistp256,diffie-hellman-group-exchange-sha256
>MACs hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com,
>umac-128-etm@openssh.com,hmac-sha2-512,hmac-sha2-256,umac-128@openssh.com
>Ciphers chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,
>aes128-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-ctr
>
>Error:
>"kex error : no match for method mac algo client->server: server [
>hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com,
>umac-128-etm@openssh.com,hmac-sha2-512,hmac-sha2-256,umac-128@openssh.com],
>client [hmac-sha1]"
>
>or sometimes
>
>"crypt_set_algorithms2: no crypto algorithm function found for
>chacha20-poly1305@openssh.com"
>
>Let me know if I can provide more information.
>
>Regards,
>*Danie de Jager*