I was in Russia a few weeks ago and due to them not recognizing the Pfizer/Moderna vaccines had to get a ton of PCR tests. All of them had QR codes on the result page. Whenever we went to a museum/or other venue that required a Russian vaccination QR code (which we didn't have due to the problem with Pfizer/Moderna recognition) they would scan the QR code on the PCR test results and it would pull up a page with the name of the person tested, time when the test was completed, and result. From my experience most places scanned the tests to confirm their validity, but when flying home to the US notably Finnair did not.