Ok have always been able to talk to my Pi via SSH from my PC until today and not sure how long it’s been broken.
All I get from putty is “Network error: Software caused connection abort”, If I try an app I have in Windows 10 it says “Server HMAC algorithm not found, Press Ctrl+R to reconnect”
I ended up uninstalling by running sudo apt-get purge openssh-server then reinstalling it sudo apt-get install openssh-server along with sudo apt-get install ssh-app-osmc then run update after.
Still didn’t work so tried Termius on my iPad which worked and connected fine.
If found this thread about a May update and then this bit:-
The immediate issue is related to a hardening of SSH in the May update that is causing problems on your system. As a temporary workaround, you should edit file /etc/ssh/sshd_config and comment out the lines:
KexAlgorithms curve25519-sha256@libssh.org,ecdh-sha2-nistp521,ecdh-sha2-nistp384,ecdh-sha2-nistp256,diffie-hellman-group-exchange-sha256
Ciphers chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes128-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-ctr
MACs hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-512,hmac-sha2-256,umac-128@openssh.com
See this2 for details of accessing the command line without SSH. Alternatively, since you’re using a Pi, you can also shutdown the machine and edit the card on another computer.
Edit: I’ve tested the new sshd_config file and it works fine on my machine. I suspect your link to Debian unstable (“sid”) might have caused unforeseen problems.
Edit 2: Sorry, I forgot to mention which file to edit, Error now fixed.
Which when I edit out now works on my PC but this says temporary, what’s the permanent fix I don’t want to leave it insecure.