SSH via guacamole

Hi !

I setup a guacamole werver in my network which holds also ssh sessions (actually 7) i have most ubuntu 20.04 or newest armbian, both things are working good. I also added now my ipfire as a session but connect always fail but i.
Entries in guacamole are correct and log of ipfire says
Jan 17 07:42:02 ipfire sshd[7212]: Unable to negotiate with port 44518: no matching host key type found. Their offer: ssh-rsa,ssh-dss [preauth]
( is the guacamole host)
any hints ?

Ciao Gerd