Problems loading a private key with passphrase encoding is AES-256-CFB

No, it does not support CFB mode for encrypted PEM files. Your best bet is to convert the file to use CBC mode instead:

openssl rsa -in key_cfb.pem -aes256 -out key_cbc.pem

You’ll have to type the key’s passphrase three times, and then you should be able to work with the output file using :public_key’s functions.