Fedora 22 to Fedora 23 upgrades OpenSSH from 6.9 to 7.1, but the release notes only mention 7.1 and don't mention the default configuration changes that happened in 7.0, such as the disabling of ssh-dss public keys that may prevent a login to/from upgraded systems without explicit command line parameters.
it only links to 7.1 release notes.
"3.4.2. OpenSSH 7.1
The OpenSSH project continues to improve the security of network communication with the release of OpenSSH 7.1. See the upstream release notes for detailed information about this release."
there should be at least a link to the OpenSSH 7.0 release notes too;
possibly explicitly mentioning the disabling of public keys.
"Support for ssh-dss, ssh-dss-cert-* host and user keys is disabled by default at run-time. To temporarily enable existing host keys, use the command line option '-oHostKeyAlgorithms=ssh-dss' and to enable existing user keys, use '-oPubkeyAcceptedKeyTypes=ssh-dss'."
Just adding, there should be also summed up content of the heads up email on devel, mentioning ssh1 support . I tried to reach you before release, according to , but without any success.
If you have further queries, feel free to reach for me here on IRC. This should be probably updated early so others updating will not get into troubles as Michael.