Ubuntu / Kubuntu 26.04 — ssh

I have a number of old and new virtual machines, and need to ssh from each VM to the host.

Therefore install an ssh server:

# apt install openssh-server

And configure it to allow incoming connections from older VMs:
Add a file /etc/ssh/sshd_config.d/allow-older-clients.conf
with contents:

# When a client ssh fails to login, look at the "service sshd status" log,
# and by use of "man sshd_config" find the options that need additional values.
Ciphers +aes128-cbc,aes192-cbc,aes256-cbc
KexAlgorithms +diffie-hellman-group1-sha1,diffie-hellman-group-exchange-sha1
HostKeyAlgorithms +ssh-rsa