Key images in Monero are something quite different to raw private keys. They are a one time use alternative public key which is used for verifying there are no double spends within the ring signature.

Feather does give you the option to restore a full wallet from your private spend key at the set up wizard. However, I would be surprised in Coinomi gives Loyce the option to export his private spend key. I suspect he would have to go through the https://coinomi.github.io/tools/bip39/ site I linked above, at which point it will be easier just to use the Monero seed phrase it generates rather than the private spend key.