It’s not like your screwdriver example at all. It’s like saying I already have my nostr private key in my iOS device and I don’t want to paste it anywhere else on any device, Android, desktop, or otherwise. I want the signer app that I have a use on my primary device to be able to sign into an...

I think it's more common then you think. I am in the same boat honesty. It's not just phones but tablets as well. There are a lot of people who have mixed environments. If signers could work like 2FA apps then there wouldn't be problem.