userauth_pubkey: signature algorithm ssh-rsa not in PubkeyAcceptedAlgorithms [preauth]
And it will not allow to connect using older, SSH-1 keys.
The temporary solution is to add
PubkeyAcceptedKeyTypes +ssh-rsa
to the /etc/ssh/sshd_config and restart the SSH daemon. Well, it’s advisable not to use weaker keys for a long time.
Thanks to the Archlinux forum for the info