The tinyssh server only uses DJB cipher suites; the [email protected] implementation has been in place for quite some time without any major issues.

https://www.libssh.org/2013/11/03/openssh-introduces-curve25...

"This algorithm does not rely on NIST-based curves and gives us more security confidence against a possible backdoor in nistp-256 curve. Today is a big day for us because OpenSSH team approved my patch and made [email protected] the default key exchange!"

Also, the original RSA keys used in SSH have a sha-1 problem, and have been deprecated.

https://www.zdnet.com/article/openssh-to-deprecate-sha-1-log...

https://www.openssh.com/releasenotes.html

    This release disables RSA signatures using the SHA-1 hash algorithm
    by default. This change has been made as the SHA-1 hash algorithm is
    cryptographically broken, and it is possible to create chosen-prefix
    hash collisions for <USD$50K [1]

    For most users, this change should be invisible and there is
    no need to replace ssh-rsa keys. OpenSSH has supported RFC8332
    RSA/SHA-256/512 signatures since release 7.2 and existing ssh-rsa keys
    will automatically use the stronger algorithm where possible.

    Incompatibility is more likely when connecting to older SSH
    implementations that have not been upgraded or have not closely tracked
    improvements in the SSH protocol.