I am trying to perform a password-less access from a Linux system to a MacOS system using SSH private / public keys

I am generating the keys on the Linux system using

ssh-keygen -t rsa -b 4096

and then copy the public key to my MacOS system using

ssh-copy-id -i id_rsa <myuserid>@<apple-system>

Then I call

ssh -v <myuserid>@<apple-system>

and I get different results when using Big Sur (Version 11.1) and Catalina (Version 10.15.7)!

On Catalina, everything works fine and I get access without a password prompt:

debug1: Authentications that can continue: publickey,password,keyboard-interactive
debug1: Next authentication method: publickey
debug1: Offering public key: /home/pi/.ssh/id_rsa RSA SHA256:MQmWsfb2P9X/LLeKfm2hG1QpnM2Fi9EaoWAnTKSSSck
debug1: Server accepts key: /home/pi/.ssh/id_rsa RSA SHA256:MQmWsfb2P9X/LLeKfm2hG1QpnM2Fi9EaoWAnTKSSSck
debug1: Authentication succeeded (publickey).

On Big Sur the same id_rsa failed:

debug1: Authentications that can continue: publickey,password,keyboard-interactive
debug1: Next authentication method: publickey
debug1: Offering public key: /home/pi/.ssh/id_rsa RSA SHA256:MQmWsfb2P9X/LLeKfm2hG1QpnM2Fi9EaoWAnTKSSSck
debug1: Authentications that can continue: publickey,password,keyboard-interactive

I checked the file permissions on both system and they are identical und also the configuration file /etc/ssh/sshd_config is the same on both systems.

Is there anything else in Big Sur, which has to be changed to allow password-less access from a remote system?

Any help is appreciated!