You mean an sshd upgrade as well. That is your problem.

I am assuming something that conforms to openSSH.

The destination node (server) sets the permissions. SFTP_UMASK is an environment variable that you can add to the sshd process on the server. It does what you think - changes permissions for sftp operations. ssh_config may have a SftpUmask setting as well. I DO NOT KNOW if this affects scp.

1. try changing ssh_config to see if it impacts what you need. Every sshd node needs this change.
2. switch to sftp, SFTP_UMASK ....I know it is a code change.
3. use scp -p ... this is a code change too.

Without getting help from your OS provider, 1, 2, 3 are pretty much your choices. The only one I know above that works is scp -p.

Maybe someone else knows a workaround.

Your choice.