I know sorry it is a typo in the heading, what I did I generated anew key pair with type and replaced the old rsa pub key on a server updated atl least from Debian 10. it is a fileserver in a multiple server ISPconfig enviorement. after that I was required to enter a password. Installing the old rsa key again ssh loging was fine again. Internet reseach said ed25519 is not supported. could not find a solution.
Debian 12 supports ed25519 keys. If you can't log in with a newly created ed25519 key, then you might have done something wrong when creating it. What debian 12 does not support anymore are very old keys that use old ciphers. So maybe you did not created a new key or you created one which uses very old encryption.
So what should be wrong ssh-keygen -t ed25519 typing just enter when asked for a similar generated key works for accesing a ISPconfig generated test website
If it works for a website you generated in ISPConfig, then the key is ok and you might have installed it wrong when installing it manually.
I edited /root/.ssh/authorized_keys deleted the old RSA key and inserted the content of .pub file, ss I did x times before on abaout a dozend seevers before succesfull. now I would replace all these old rsa keys with the recommended new ed25519 keys and failed on the first server.
now I generated a new one without changeing filename and it works. But I need more key pairs for different servers. As I know that is possible with different filenames or am i wrong.
