Testing Gitlab ci cd how to solve "the connection is refused" "no matching host key type found" - continuous-integration

Question

Gitlab CI/CD can't connect to my remote vps.
I took https://gitlab.com/gitlab-examples/ssh-private-key as an example to make a .gitlab-ci.yaml file, its contents:
image: ubuntu
before_script:
- 'which ssh-agent || ( apt-get update -y && apt-get install openssh-client git -y )'
- eval $(ssh-agent -s)
- echo "$SSH_KEY_VU2NW" | tr -d '\r' | ssh-add -
- mkdir -p ~/.ssh
- chmod 700 ~/.ssh
- ssh-keyscan (domain name here) >> ~/.ssh/known_hosts
- chmod 644 ~/.ssh/known_hosts
Test SSH:
script:
- ssh root#(IP address here)
The runner responds with
the connection is refused
The server auth log says
sshd[2222]: Unable to negotiate with XXXXX port 53068: no matching
host key type found. Their offer: sk-ecdsa-sha2-nistp256#openssh.com
[preauth]
sshd[2220]: Unable to negotiate with XXXXX port 53068: no
matching host key type found. Their offer: sk-ssh-ed25519#openssh.com
[preauth]
Is there any way to solve this? I already tried connecting to another VPS, also without luck.

Answer 1

Finally got it to work, with this contents in the .gitlab-ci.yaml file:
image: ubuntu
before_script:
- 'which ssh-agent || ( apt-get update -y && apt-get install openssh-client git -y )'
- eval $(ssh-agent -s)
- mkdir -p /root/.ssh
- chmod 700 /root/.ssh
- echo "$SSH_KEY_GITLAB" >> /root/.ssh/id_rsa
- ssh-keyscan DOMAINNAME >> /root/.ssh/known_hosts
- chmod 644 ~/.ssh/known_hosts
- chmod 400 ~/.ssh/id_rsa
Test SSH:
script:
- ssh root#DOMAINNAME
Where $SSH_KEY_GITLAB is set in Gitlabs' Settings > CICD section, and is a private key, generated by Putty, converted in Putty to an open SSH key.
The public version of this key must be in the target hosts' ~/.ssh/authorized_keys
...and DOMAINNAME must be a domain that resides on the target host, or, the DNS record should point there anyhow.
With ssh -vvv came some debugging info that pointed to the checking of ~/.ssh/id_rsa, so that's where I put the private key.