Disable pre-authentication compression
The openssh disabled pre-authentication compression (the one called just gzip) in OpenSSH 7.4 (in 2016) in favor of the gzip@openssh.com, which is turned on only after the authentication is done.
The compression is not enabled by default, but some poeple have old configuration files or think this will speed stuff for them. We should probably follow the suit and disable/remove the support for this too sooner or later.