Not all countries yet offer a digital vaccination certificate (passport) for COVID-19 but only a PDF certificate that can be printed on paper.
However, it is possible, completely free of charge, to create a digital COVID-19 certificate for easy use in your Android or iPhone by using a new service from YourPass.
If you have an iPhone, you can save the certificate in Wallet, if you have Android, the free app YourPass YourWallet is recommended (important, install before you create the certificate).
Go to the service and follow the instructions https://www.getcovidpass.eu
NOTE! Always save the PDF certificate in your mobile for safety!
For those of you who have an iPhone, there is also the same service from https://covidpass.marvinsextro.de (Importantly, use Safari Browser for that link if you have iOS).