Comment 4 for bug 1822370

Maybe the keepalive defaults got changed?
All past references to the issue refer to some sort of keepalive to avoid the issue.
For example [1]

Be aware that some suggestions on [1] configure the sever, while your issue is on the client side (at least that is where the upgrade happened.

You could also run your failing ssh connection with debug enabled, sometimes a message helps to identify the issue
$ ssh -vvv x.x.x.x

You could check if the defaults changed by comparing your old and new setup with -G like:
$ ssh -G x.x.x.x
That will report the configs used.

I compared 18.10 and 19.04 and found those:
$ diff ssh.old ssh.new
3a4
> addkeystoagent false
36d36
< useprivilegedport no
47,49c47,50
< hostkeyalgorithms <email address hidden>,<email address hidden>,<email address hidden>,<email address hidden>,<email address hidden>,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
< hostbasedkeytypes <email address hidden>,<email address hidden>,<email address hidden>,<email address hidden>,<email address hidden>,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
< kexalgorithms curve25519-sha256,<email address hidden>,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha256,diffie-hellman-group14-sha1
---
> hostkeyalgorithms <email address hidden>,<email address hidden>,<email address hidden>,<email address hidden>,<email address hidden>,<email address hidden>,<email address hidden>,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
> hostbasedkeytypes <email address hidden>,<email address hidden>,<email address hidden>,<email address hidden>,<email address hidden>,<email address hidden>,<email address hidden>,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
> kexalgorithms curve25519-sha256,<email address hidden>,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group14-sha256,diffie-hellman-group14-sha1
> casignaturealgorithms ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
52c53
< pubkeyacceptedkeytypes <email address hidden>,<email address hidden>,<email address hidden>,<email address hidden>,<email address hidden>,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
---
> pubkeyacceptedkeytypes <email address hidden>,<email address hidden>,<email address hidden>,<email address hidden>,<email address hidden>,<email address hidden>,<email address hidden>,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
68c69
< ipqos lowdelay throughput
---
> ipqos af21 cs1
70a72
> syslogfacility USER

I see nothing obvious, if anything then the change to ipqos from
< ipqos lowdelay throughput
to
> ipqos af21 cs1

This might be interesting since one of the messages at [1] said [2]
 $ ssh -o IPQoS=throughput user@host

Could you try if that resolves your issue.
If yes we need to find why the default was changed and if we want to revert it or not.

[1]: https://askubuntu.com/questions/127369/how-to-prevent-write-failed-broken-pipe-on-ssh-connection
[2]: https://askubuntu.com/a/1112674/532139