Gitlab personal server: Permission denied (publickey) - gitlab

Question

I have installed a Gitlab server (15.1) and try to finalize configuration for my user.
I am able to connect with ssh to the server for administration purpose.with my user. I use rsa key pair for that. I connect on the 22002 port and everything works well.
Now I wanted to follow Gitlab instruction to create a project, a new pair of key and connect my repository to Gitlab using this key pair.
I have created keys (ed25519), copy the public part into the Gitlab web server and just try the command ssh -T myuser#gitlab.mydomain.com
I get the following result:
Permission denied (publickey)
I have searched for hours but didn't find what I have made wrong.
If I run ssh -Tvvv myuser#gitlab.mydomain.com I get the following result:
OpenSSH_9.0p1 Debian-1+b1, OpenSSL 3.0.4 21 Jun 2022
debug1: Reading configuration data /home/tasseb/.ssh/config
debug1: /home/tasseb/.ssh/config line 19: Applying options for gitlab-kb
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: include /etc/ssh/ssh_config.d/*.conf matched no files
debug1: /etc/ssh/ssh_config line 21: Applying options for *
debug1: Connecting to gitlab.mydomain.com [160.53.247.6] port 22002.
debug1: Connection established.
debug1: identity file /home/tasseb/.ssh/id_ed25519-gitlab type 3
debug1: identity file /home/tasseb/.ssh/id_ed25519-gitlab-cert type -1
debug1: Local version string SSH-2.0-OpenSSH_9.0p1 Debian-1+b1
debug1: Remote protocol version 2.0, remote software version OpenSSH_8.4p1 Debian-5+deb11u1
debug1: compat_banner: match: OpenSSH_8.4p1 Debian-5+deb11u1 pat OpenSSH* compat 0x04000000
debug1: Authenticating to gitlab.mydomain.com:22002 as 'sbe'
debug1: load_hostkeys: fopen /home/tasseb/.ssh/known_hosts2: No such file or directory
debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts: No such file or directory
debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts2: No such file or directory
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: algorithm: curve25519-sha256
debug1: kex: host key algorithm: ssh-ed25519
debug1: kex: server->client cipher: chacha20-poly1305#openssh.com MAC: <implicit> compression: none
debug1: kex: client->server cipher: chacha20-poly1305#openssh.com MAC: <implicit> compression: none
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: SSH2_MSG_KEX_ECDH_REPLY received
debug1: Server host key: ssh-ed25519 SHA256:ofs8tNkzOxuU5AwC2VYbFGPXfERPKXGOFrTatb8hV78
tlab.mydomain.com]:22002
debug1: load_hostkeys: fopen /home/tasseb/.ssh/known_hosts2: No such file or directory
debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts: No such file or directory
debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts2: No such file or directory
debug1: Host '[gitlab.mydomain.com]:22002' is known and matches the ED25519 host key.
debug1: Found key in /home/tasseb/.ssh/known_hosts:4
debug1: rekey out after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: rekey in after 134217728 blocks
debug1: get_agent_identities: bound agent to hostkey
debug1: get_agent_identities: ssh_fetch_identitylist: agent contains no identities
debug1: Will attempt key: /home/tasseb/.ssh/id_ed25519-gitlab ED25519 SHA256:7BtjWt7Ysd40SJ1xX1sBlZb7PJqUW5K2NhxDBvtIgfY explicit 7
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_input_ext_info: server-sig-algs=<ssh-ed25519,sk-ssh-ed25519#openssh.com,ssh-rsa,rsa-sha2-256,rsa-sha2-512,ssh-dss,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,sk-ecdsa-sha2-nistp256#openssh.com,webauthn-sk-ecdsa-sha2-nistp256#openssh.com>
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey
debug1: Next authentication method: publickey
debug1: Offering public key: /home/tasseb/.ssh/id_ed25519-gitlab ED25519 SHA256:7BtjWt7Ysd40SJ1xX1sBlZb7PJqUW5K2NhxDBvtIgfY explicit
debug1: Authentications that can continue: publickey
debug1: No more authentication methods to try.
sbe#gitlab.mydomain.com: Permission denied (publickey).
Thanks for your help.

Answer 1

I was sure it was something simple that I have omitted.
So this morning I just continue to set up locally my git project and did the first push using my user and password. That has working well.
Then, I edit my .ssh/config file, changing my username by "git" as suggested by #VonC.
Re run the test, it asked for the passphrase for the key and everything is ok.
I thought I could set up the ssh before doing a first push or set the origin locally, but it seems no.
Thanks again for your precious comments.

Answer 2

Using SSH URL with a GitLab on-premise server should always involve the technical account git, not "myuser".
See "Verify that you can connect"
ssh -Tvvv git#gitlab.mydomain.com
GitLab will authenticate you through the public key registered to the GitLab user account SSH setting page.