It appears that sntrup4591761x25519-sha512@tinyssh.org was removed from OpenSSH, and replaced with sntrup761x25519-sha512@openssh.com, at the behest of Daniel J. Bernstein.
"Per the authors, sntrup4591761 was replaced almost two years ago by sntrup761."
It appears that sntrup4591761x25519-sha512@tinyssh.org was removed from OpenSSH, and replaced with sntrup761x25519-sha512@openssh.com, at the behest of Daniel J. Bernstein.
Can this key exchange be implemented in tinyssh?
https://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.bin/ssh/kexsntrup761x25519.c