See https://www.openssh.com/releasenotes.html#9.0p1 for the release notes.

Please read https://www.openssh.com/report.html for bug reporting
instructions and note that we do not use Github for bug reporting or
patch/pull-request management.

This is the port of OpenBSD's excellent OpenSSH[0] to Linux and other
Unices.

OpenSSH is based on the last free version of Tatu Ylonen's sample
implementation with all patent-encumbered algorithms removed (to
external libraries), all known security bugs fixed, new features
reintroduced and many other clean-ups.  OpenSSH has been created by
Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo de Raadt,
and Dug Song. It has a homepage at https://www.openssh.com/

This port consists of the re-introduction of autoconf support, PAM
support, EGD/PRNGD support and replacements for OpenBSD library
functions that are (regrettably) absent from other unices. This port
has been best tested on AIX, Cygwin, HP-UX, Linux, MacOS/X,
FreeBSD, NetBSD, OpenBSD, OpenServer, Solaris and UnixWare.

This version actively tracks changes in the OpenBSD CVS repository.

The PAM support is now more functional than the popular packages of
commercial ssh-1.2.x. It checks "account" and "session" modules for
all logins, not just when using password authentication.

There is now several mailing lists for this port of OpenSSH. Please
refer to https://www.openssh.com/list.html for details on how to join.

Please send bug reports and patches to https://bugzilla.mindrot.org or
the mailing list openssh-unix-dev@mindrot.org.  To mitigate spam, the
list only allows posting from subscribed addresses.  Code contribution
are welcomed, but please follow the OpenBSD style guidelines[1].

Please refer to the INSTALL document for information on dependencies and
how to install OpenSSH on your system.

Damien Miller <djm@mindrot.org>

Miscellania -

This version of OpenSSH is based upon code retrieved from the OpenBSD CVS
repository which in turn was based on the last free sample implementation
released by Tatu Ylonen.

References -

[0] https://www.openssh.com/
[1] https://man.openbsd.org/style.9