OpenSSH_6.7p1 hostbased authentication failing on linux->linux connection. what's wrong with my config?

[grantksupport at operamail.com]

@client

as root (as before)

	ssh server.DOMAIN.COM
		Permission denied (hostbased).

instead, as my user, fails differently for some reason,

	ssh server.DOMAIN.COM
		...
		no matching hostkey found for key ED25519 xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx
		ssh_keysign: no reply
		key_sign failed
		Permission denied (hostbased).

and verbose

	ssh server.DOMAIN.COM -vvv
		...
		debug1: Authentications that can continue: hostbased
		debug3: start over, passed a different list hostbased
		debug3: preferred hostbased
		debug3: authmethod_lookup hostbased
		debug3: authmethod_is_enabled hostbased
		debug1: Next authentication method: hostbased
		debug2: userauth_hostbased: chost client.DOMAIN.COM.
		debug2: ssh_keysign called
		debug3: ssh_msg_send: type 2
		debug3: ssh_msg_recv entering
		debug1: permanently_drop_suid: 1000
		debug2: we sent a hostbased packet, wait for reply
		debug1: Authentications that can continue: hostbased
		debug2: userauth_hostbased: chost client.DOMAIN.COM.
		debug2: ssh_keysign called
		debug3: ssh_msg_send: type 2
		debug3: ssh_msg_recv entering
		debug1: permanently_drop_suid: 1000
		debug2: we sent a hostbased packet, wait for reply
		debug1: Authentications that can continue: hostbased
		debug2: userauth_hostbased: chost client.DOMAIN.COM.
		debug2: ssh_keysign called
		debug3: ssh_msg_send: type 2
		debug3: ssh_msg_recv entering
		debug1: permanently_drop_suid: 1000
		debug2: we sent a hostbased packet, wait for reply
		debug1: Authentications that can continue: hostbased
		debug2: userauth_hostbased: chost client.DOMAIN.COM.
		debug2: ssh_keysign called
		debug3: ssh_msg_send: type 2
		debug3: ssh_msg_recv entering
		debug1: permanently_drop_suid: 1000
		no matching hostkey found for key ED25519 xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx
		ssh_keysign: no reply
		key_sign failed
		debug2: we did not send a packet, disable method
		debug1: No more authentication methods to try.
		Permission denied (hostbased).