https://askubuntu.com/questions/836048/ssh-returns-no-matching-host-key-type-found-their-offer-ssh-dss

SSH returns: no matching host key type found
============================================

ssh root@192.168.178.126
returns:
"Unable to negotiate with 192.168.178.126 port 22: no matching host key type found. Their offer: ssh-rsa,ssh-dss"


- In a nutshell, you should add the option -oHostKeyAlgorithms=+ssh-dss to the SSH command:
     ssh -oHostKeyAlgorithms=+ssh-dss root@192.168.8.109


- You can also add a host pattern in your ~/.ssh/config so you don't have to 
specify the key algorithm every time:

Host nas
  HostName 192.168.8.109
  HostKeyAlgorithms=+ssh-dss

This has the added benefit that you don't need to type out the IP address. 
Instead, ssh will recognize the host nas and know where to connect to.
Of course you can use any other name in its stead.


- Editing the ~/.ssh/config file is the best option. If you have a number of 
hosts to connect to on the same subnet you can use the following method to 
avoid entering each host in the file:

 Host 192.168.8.*
  HostKeyAlgorithms=+ssh-dss

This works great for me as I have a number of Brocade switches to manage and 
they started complaining about the Host key after I moved to Ubuntu 16.04.


- The latest OpenSSH version disables RSA, if you run into the error now, you 
should use +ssh-rsa instead of +ssh-dss – 
Fabian Schmengler
Commented Oct 11, 2021 at 8:27


-------
- big explanation:
http://www.openssh.com/legacy.html