Trying to restrict my SSH server access to 'private ssh key only'

Question

Good Morning, I need to force my SSH server to deny any connection which doesn't have my private SSH key... and not to ask a password

My /etc/ssh/sshd_config:

Include /etc/ssh/sshd_config.d/*.conf
Port 22
#AddressFamily any
#ListenAddress 0.0.0.0
#ListenAddress ::
#HostKey /etc/ssh/ssh_host_rsa_key
#HostKey /etc/ssh/ssh_host_ecdsa_key
#HostKey /etc/ssh/ssh_host_ed25519_key
Ciphers and keying
#RekeyLimit default none
Logging
#SyslogFacility AUTH
#LogLevel INFO
Authentication:
#LoginGraceTime 2m
#PermitRootLogin prohibit-password
#StrictModes yes
#MaxAuthTries 7
#MaxSessions 3
PubkeyAuthentication no
Expect .ssh/authorized_keys2 to be disregarded by default in future.
AuthorizedKeysFile  ~/.ssh/authorized_keys ~/.ssh/authorized_keys2
#AuthorizedPrincipalsFile none
#AuthorizedKeysCommand none
#AuthorizedKeysCommandUser nobody
For this to work you will also need host keys in /etc/ssh/ssh_known_hosts
#HostbasedAuthentication no
Change to yes if you don't trust ~/.ssh/known_hosts for
HostbasedAuthentication
#IgnoreUserKnownHosts no
Don't read the user's ~/.rhosts and ~/.shosts files
#IgnoreRhosts yes
To disable tunneled clear text passwords, change to no here!
PasswordAuthentication no
PermitEmptyPasswords no
Change to yes to enable challenge-response passwords (beware issues with
some PAM modules and threads)
ChallengeResponseAuthentication no
Kerberos options
#KerberosAuthentication no
#KerberosOrLocalPasswd yes
#KerberosTicketCleanup yes
#KerberosGetAFSToken no
GSSAPI options
#GSSAPIAuthentication no
#GSSAPICleanupCredentials yes
#GSSAPIStrictAcceptorCheck yes
#GSSAPIKeyExchange no
Set this to 'yes' to enable PAM authentication, account processing,
and session processing. If this is enabled, PAM authentication will
be allowed through the ChallengeResponseAuthentication and
PasswordAuthentication.  Depending on your PAM configuration,
PAM authentication via ChallengeResponseAuthentication may bypass
the setting of "PermitRootLogin without-password".
If you just want the PAM account and session checks to run without
PAM authentication, then enable this but set PasswordAuthentication
and ChallengeResponseAuthentication to 'no'.
UsePAM yes
#AllowAgentForwarding yes
#AllowTcpForwarding yes
#GatewayPorts no
X11Forwarding yes
#X11DisplayOffset 10
#X11UseLocalhost yes
#PermitTTY yes
PrintMotd no
#PrintLastLog yes
#TCPKeepAlive yes
#PermitUserEnvironment no
#Compression delayed
#ClientAliveInterval 0
#ClientAliveCountMax 3
#UseDNS no
#PidFile /var/run/sshd.pid
#MaxStartups 10:30:100
#PermitTunnel no
#ChrootDirectory none
#VersionAddendum none
no default banner path
#Banner none
Allow client to pass locale environment variables
AcceptEnv LANG LC_*
override default of no subsystems
Subsystem   sftp    /usr/lib/openssh/sftp-server
Example of overriding settings on a per-user basis
#Match User anoncvs
X11Forwarding no
AllowTcpForwarding no
PermitTTY no
ForceCommand cvs server

Match Address 127.0.0.*
    PubkeyAuthentication yes
Match Address 192.168.1.*
    PubkeyAuthentication yes

when i try ssh -i "/path/to/ssh-key-private.txt" john@localhost it results in

john@localhost's password: 
Permission denied, please try again.
john@localhost's password: 
Permission denied, please try again.
john@localhost's password: 
Received disconnect from ::1 port 22:2: Too many authentication failures
Disconnected from ::1 port 22

and when i change PubkeyAuthentication to yes

john@localhost: Permission denied (publickey)

please note that i had already tried the following https://askubuntu.com/a/974566/1067284 https://askubuntu.com/a/1335082/1067284 and nothing worked...