One option could be to make click on QR-code open the nostrconnect:// url on mobile in addition to copying it to clipboard.
I'm not sure that would ever happen, since if they have a mobile signer they will choose nip 55 right? Which I want to encourage, so friction here seems good.
I open flotilla in mobile browser and nip55 isn't useful, I have Amber, I want to use it - why not open it with 1 click?