Unless your MacBook is 20 years old, something else is going on. Are you perhaps on 100Mb/s link? With overhead 10MB/s is about what one would expect on a 100Mb

Unless your MacBook is 20 years old, something else is going on. Are you perhaps on 100Mb/s link? With overhead 10MB/s is about what one would expect on a 100Mb/s link. Even without hardware acceleration my 2018 Mac Mini, which is much slower than my 2020 MBA using ARM, does much better than that--64MB/s, but that's a floor as the file itself is only 64MB. I tested by forcing chacha20-poly1305, which wouldn't be 6x faster than software-only aes128-gcm or aes256-gcm. Also, though /usr/bin/ssh on macOS is compiled with libressl, and there was a brief post-fork period when libressl lacked accelerated cipher implementations, it has supported AES-NI for quite awhile. I'm sensitive to these things as I still run a few PC Engines APUs and force aes256-gcm in sshd_config; by default OpenSSH prefers chacha20-poly1305. To an APU I get 30MB/s with AES-NI aes256-gcm, and 10MB/s with chacha20-poly1305. The APU has an AMD GX-412TC, which came out in 2013 but as a low-powered embedded part has the performance of something 5 or 10 years older.