Thanks so much for your help. I actually found that thread on my way to find the solution and have run across a few of your other posts in solving my subsequent problems, so I am very grateful for all you do. (I try to only post things when I'm really stuck, but the last time I used a mac was 1994 and the learning curve has been a bit steep to say the least.)

I've managed to solve Error1 and Error3 in one go by following this: https://developer.apple.com/forums/thread/733942 specifically: Add the following to your .entitlements: A com.apple.application-identifier property whose value is your App ID A com.apple.developer.team-identifier property whose value is your Team ID both ARM and Intel are now victims of Error2, which I suppose is reassuring. Still not sure where com.apple.quarantine extended file attributes are coming from.