scp and rsync

Have you set up ssh keys on your rpi5?

Most likely generating a new host key on the MacBook, using a less broken algorithm, will be sufficient. With that in mind:

• What SSH version do you have on the MacBook? To find out: ssh -V
• What host keys do you already have? To find out: ls -l /etc/ssh

Read the error message, this is about host keys on the Mac, not the user keys on the Pi.

The message isn't great.

I assume you mean it is about SHA-1 being deprecated for use with RSA, in OpenSSH 8.2. That SHA-1 is not actually part of the key, only a hash used to sign the key. I think you explained this a year or two ago. The point being that SHA-1 is an attribute of the SSH software, not the RSA key.

I did wonder, but assumed a MAC would automatically update its SSH software. I'm still not sure if this is what you are getting at. Maybe the fact it is still offering ssh=dss is the smoking gun, a sign of old software?

This is Apple, remember. As with Bash and GCC and Python and others, they’re probably allergic to the licence in the new version or something.

Under normal circumstances SSH updates accompany macOS updates.

Current macOS has OpenSSH 9.4, i.e. August last year. But what matters here is what the OP is actually running and they’ve not yet shared that information as far as I can see.

I ran into the same problem with the VLC mobile app when trying to connect to the buster-upgraded RPi I have managing podcasts for me. Did a bit of searching and settled on this solution:

pi@media:~ $ cat /etc/ssh/sshd_config.d/vlc.conf HostkeyAlgorithms +ssh-rsa,ssh-dss