[PROBLEM] Where is my SSH private key so i can use it to login Xbian via FileZilla?

[stripechange]

The file you're looking for is not necessarily a PEM or PPK file, but rather an OpenSSH private key file, which is typically named id_rsa or id_ed25519.

By default, the OpenSSH private key file is stored in the ~/.ssh directory of the user account that generated the key. In your case, since you have SSH passwordless access to the Xbian root account, you can assume that the private key file is stored in /root/.ssh on the Xbian machine.

However, it's not actually there! The reason is that id_rsa and id_ed25519 files are usually generated by ssh-keygen and are not stored in the default locations. Instead, they are generated in a temporary directory and then moved to the ~/.ssh directory.

To find the location of your private key file, you can try the following:

Run ssh-keygen -L -f /root/.ssh/id_rsa (or id_ed25519) on the Xbian machine. This will list the files that are referenced by the key. If you find a file with a name like id_rsa or id_ed25519, that's likely your private key file.
Run find /root -name id_rsa (or id_ed25519) on the Xbian machine to search for files with those names recursively. moto x3m
Check your ~/.ssh directory on your Debian user PC to see if you have a copy of the private key file there. If you do, you can use it to connect to Xbian using FileZilla.
Once you find the location of your private key file, you can use it in FileZilla by selecting "OpenSSH Private Key" as the authentication method and specifying the path to the file.