I am against domestic passports for definite. Morally I think they are wrong but they are also impractical. I was in Italy recently where we had to present proof of vaccine for all tourist activities, transport and eating/drinking indoors. They checked for them at around 90% of the places I went to but for most its obviously just a checkbox exercise. One place they asked for photographic ID alongside my vaccine, the names did not match (maiden vs married name) but I was permitted in no problem. A few times I showed my QR code on my phone, the staff member waved their device over it but did not verify it. It added so much time and effort, a literal duplication of staffing for major attractions i.e. one person checking tickets, one person checking vaccine info/neg tests.