ssh_dispatch_run_fatal: incorrect signature

An errata from October 29, 2024 for OpenBSD 7.6 fixed a problem with
OpenSSH on big-endian platforms (like macppc and powerpc64),

  https://www.openbsd.org/errata76.html

If a big-endian machine doesn't have the errata fix, ssh might fail
with an error,

$ ssh 192.168.0.112
ssh_dispatch_run_fatal: Connection to 192.168.0.112 port 22: incorrect signature

One can work around the problem by removing mlkem768x25519-sha256 from
KexAlgorithms,

$ ssh -o KexAlgorithms='-mlkem*' 192.168.0.112