I'm saying the primary gateway most iOS users are using for loading a QR code - the camera app - will not present a transition to load your URL in this situation
Whether the resulting HTML game is playable in Safari is a different discussion.
The QR code, as generated, is effectively "not clickable" for most iOS users, unless they are using something other than the most common way to read QR codes on their phone like a 3rd party QR code reading app or similar.
In 2016, that laptop also came with System Integrity Protection - you couldn't change /usr/bin/python if you wanted to. And you still can't to this very day. Changing System-provided python was always against recommendations in prior OS versions because the next OS update could re-replace it at any time.
I agree that it probably contributed to python 2 inertia as it was re-exposing people to the idea that "typing python in the Terminal gets me python 2" and "I just used what I already had" - but it definitely wasn't stopping people installing a newer version.
I think Apple stopped loading the passphrases into the agent automatically. I think they're strictly only loaded from the keychain now, per connection, unless you explicitly use -A to add them to the agent.
The next time you'd like to diagnose, you can reboot into Recovery and use "csrutil enable --without dtrace --without debug" and you should be able to avoid those issues.
In prior versions, it was stored in Login keychain, which was not synchronized.
Additionally, the items were visible in the security command line tool and in Keychain Access, so you could delete them.
The Local Items keychain / iCloud Keychain is a new style keychain that was back ported from iOS. The security and Keychain Access tools have no visibility into it, it's 100% handled by the secd service.
Edit: Ah, sorry, you meant in Sierra specifically. Yes. But I'll leave these clarifying details here for posterity :)
Edit2: Additional detail - in prior OSes, there was a GUI prompt asking if you wanted to store the passphrase in the keychain. This is gone now. It just does it (unless you preemptively edited the ssh config file to disable keychain storage in advance)
Edit3: Can confirm that "ssh-add -K -d" does in fact delete the passphrase from the keychain, even though it may throw an agent error.
https://support.apple.com/guide/security/contents-a-localpol...
The manpage for the command provides information on credential usage on Apple Silicon devices.