Change your ssh pub key on all systems

change_ssh_pub_key.sh

#!/bin/bash -xe
NEW_PUB_KEY="$HOME/.ssh/id_ed25519.pub"
OLD_PUB_KEY="$HOME/.ssh/id_rsa.pub"
NEW_PUB_KEY_STR=$(cat ${NEW_PUB_KEY})
OLD_PUB_KEY_STR=$(cat ${OLD_PUB_KEY} | cut -d' ' -f2)

for IP in $(cat ip-list-ssh.txt); do
    # Backup authorized_keys
    ssh ${USER}@${IP} "cp ~/.ssh/authorized_keys{,.bak}"
    # Add new key to authorized_keys
    ssh ${USER}@${IP} "echo ${NEW_PUB_KEY_STR} >> ~/.ssh/authorized_keys"
    # Test new key
    if ssh -o IdentitiesOnly=yes -i ${NEW_PUB_KEY} ${USER}@${IP} 'exit'; then
        # Remove old key (with or without comments)
        ssh ${USER}@${IP} "grep -v '${OLD_PUB_KEY_STR}' ~/.ssh/authorized_keys > /tmp/authorized_keys"
        ssh ${USER}@${IP} "mv /tmp/authorized_keys ~/.ssh/authorized_keys"
    else
        echo "FAILED: ${USER}@${IP}"
        ssh ${USER}@${IP} "mv ~/.ssh/authorized_keys{.bak,}"
    fi
done

Create a ip-list-ssh.txt with e.g. nmap 192.168.1.0/24 -Pn -p 22 --open -oG - | grep "/open" | awk '{ print $2 }' > ip-list-ssh.txt
Than run bash -xe ./change_ssh_pub_key.sh