What is the meaning of this line from ssh output: 'Authenticator provider $SSH_SK_PROVIDER did not resolve; disabling'?

Question

Everything works, ssh connects using private-public ssh key pair.
Just few things in ssh -v Ora2 output isn't clear for me.

This is complete ssh -v Ora2 output:

PS C:\Users\roeslermichal> ssh -v Ora2
OpenSSH_for_Windows_8.6p1, LibreSSL 3.4.3
debug1: Reading configuration data C:\\Users\\roeslermichal/.ssh/config
debug1: C:\\Users\\roeslermichal/.ssh/config line 19: Applying options for Ora2
debug1: Authenticator provider $SSH_SK_PROVIDER did not resolve; disabling
debug1: Connecting to 10.32.81.218 [10.32.81.218] port 22.
debug1: Connection established.
debug1: identity file C:\\Users\\roeslermichal\\.ssh\\poczt_id_ed25519 type 3
debug1: identity file C:\\Users\\roeslermichal\\.ssh\\poczt_id_ed25519-cert type -1
debug1: Local version string SSH-2.0-OpenSSH_for_Windows_8.6
debug1: Remote protocol version 2.0, remote software version OpenSSH_8.0
debug1: compat_banner: match: OpenSSH_8.0 pat OpenSSH* compat 0x04000000
debug1: Authenticating to 10.32.81.218:22 as 'michal'
debug1: load_hostkeys: fopen C:\\Users\\roeslermichal/.ssh/known_hosts2: No such file or directory
debug1: load_hostkeys: fopen __PROGRAMDATA__\\ssh/ssh_known_hosts: No such file or directory
debug1: load_hostkeys: fopen __PROGRAMDATA__\\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: [email protected] MAC: <implicit> compression: none
debug1: kex: client->server cipher: [email protected] 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:jQ2i6lqzzZnhdPc+GKQCS6iiCD5W/2wDzhLvigIlytg
debug1: load_hostkeys: fopen C:\\Users\\roeslermichal/.ssh/known_hosts2: No such file or directory
debug1: load_hostkeys: fopen __PROGRAMDATA__\\ssh/ssh_known_hosts: No such file or directory
debug1: load_hostkeys: fopen __PROGRAMDATA__\\ssh/ssh_known_hosts2: No such file or directory
debug1: Host '10.32.81.218' is known and matches the ED25519 host key.
debug1: Found key in C:\\Users\\roeslermichal/.ssh/known_hosts:10
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: pubkey_prepare: ssh_get_authentication_socket: No such file or directory
debug1: Will attempt key: C:\\Users\\roeslermichal\\.ssh\\poczt_id_ed25519 ED25519 SHA256:eQBpsX9pvzP6RuorzRWhlK2s4sOEdj3KrgME3TGeSMU explicit
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_input_ext_info: server-sig-algs=<ssh-ed25519,ssh-rsa,rsa-sha2-256,rsa-sha2-512,ssh-dss,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521>
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey
debug1: Next authentication method: publickey
debug1: Offering public key: C:\\Users\\roeslermichal\\.ssh\\poczt_id_ed25519 ED25519 SHA256:eQBpsX9pvzP6RuorzRWhlK2s4sOEdj3KrgME3TGeSMU explicit
debug1: Server accepts key: C:\\Users\\roeslermichal\\.ssh\\poczt_id_ed25519 ED25519 SHA256:eQBpsX9pvzP6RuorzRWhlK2s4sOEdj3KrgME3TGeSMU explicit
debug1: Authentication succeeded (publickey).
Authenticated to 10.32.81.218 ([10.32.81.218]:22).
debug1: channel 0: new [client-session]
debug1: Requesting [email protected]
debug1: Entering interactive session.
debug1: pledge: filesystem full
debug1: ENABLE_VIRTUAL_TERMINAL_INPUT is supported. Reading the VTSequence from console
debug1: ENABLE_VIRTUAL_TERMINAL_PROCESSING is supported. Console supports the ansi parsing
debug1: client_input_global_request: rtype [email protected] want_reply 0
debug1: client_input_hostkeys: searching C:\\Users\\roeslermichal/.ssh/known_hosts for 10.32.81.218 / (none)
debug1: client_input_hostkeys: searching C:\\Users\\roeslermichal/.ssh/known_hosts2 for 10.32.81.218 / (none)
debug1: client_input_hostkeys: hostkeys file C:\\Users\\roeslermichal/.ssh/known_hosts2 does not exist
debug1: client_input_hostkeys: no new or deprecated keys from server
debug1: Remote: /home/michal/.ssh/authorized_keys:1: key options: agent-forwarding port-forwarding pty user-rc x11-forwarding
debug1: Remote: /home/michal/.ssh/authorized_keys:1: key options: agent-forwarding port-forwarding pty user-rc x11-forwarding
Activate the web console with: systemctl enable --now cockpit.socket

I understand most of it, but few lines require some explanation.

1. Authenticator provider $SSH_SK_PROVIDER did not resolve; disabling
   I don't understand what $SSH_SK_PROVIDER is, and what wasn't resolved at this stage.
   What is getting disabled??
   I mean, ssh just read ssh config file from my Windows 11 laptop and applied Ora2 settings.
   It's not even connected yet, so what authentication are we talking about so early in the process.
   What $SSH_SK_PROVIDER is ?
2. Please explain these two lines for me:
   SSH2_MSG_KEXINIT sent
   SSH2_MSG_KEXINIT received
   I don't know what SSH2_MSG_KEXINIT is?
   Is it necessary?
   I'm just using private-public key pair authentication.
   Can I turn SSH2_MSG_KEXINIT off??