They removing some key types today, as was mentioned above [1][2], maybe you were hit by that.

  November 4, 2026: We’ll have a brownout of the removal of the ssh-rsa signature type (i.e., RSA keys using SHA-1) and the diffie-hellman-group-exchange-sha256 key exchange algorithm.

[2] https://github.blog/changelog/2026-09-22-security-improvemen...