Debian Stretch 9.6: openssh-server and old dropbear client don't work togheter

[owl700 at gmail.com]

Hi, I have compatibility issues with the latest version of
openssh-server and an old dropbear client, the dopbear client stops at
preauth

ov 22 14:34:03  myhostname sshd[3905]: debug1: Client protocol version
2.0; client software version dropbear_0.46
Nov 22 14:34:03 myhostname sshd[3905]: debug1: no match: dropbear_0.46
Nov 22 14:34:03 myhostname sshd[3905]: debug1: Local version string
SSH-2.0-OpenSSH_7.4p1 Debian-10+deb9u4
Nov 22 14:34:03 myhostname sshd[3905]: debug1: Enabling compatibility
mode for protocol 2.0
Nov 22 14:34:03 myhostname sshd[3905]: debug2: fd 3 setting O_NONBLOCK
Nov 22 14:34:03 myhostname sshd[3905]: debug2: Network child is on pid 3906
Nov 22 14:34:03 myhostname sshd[3905]: debug3: preauth child monitor started
Nov 22 14:34:03 myhostname sshd[3905]: debug3: privsep user:group
106:65534 [preauth]
Nov 22 14:34:03 myhostname sshd[3905]: debug1: permanently_set_uid:
106/65534 [preauth]
Nov 22 14:34:03 myhostname sshd[3905]: debug1: list_hostkey_types:
ssh-rsa,rsa-sha2-512,rsa-sha2-256,ecdsa-sha2-nistp256 [preauth]
Nov 22 14:34:03 myhostname sshd[3905]: debug3: send packet: type 20 [preauth]
Nov 22 14:34:03 myhostname sshd[3905]: debug1: SSH2_MSG_KEXINIT sent [preauth]

Can you help?

Thanks