score:6
I'm not sure if this is the answer you're looking for but after doing some research I am unable to find any source that states the exact format of the certificate, i.e. if a digital scan/photo of the certificate from the GP is acceptable. But here's what I found.
According to the gov.uk website if a UK resident wishes to travel to Austria from the UK, he/she "... must be able to present at the border a medical certificate with micro-biological test results in English, French, German or Italian which is no more than 4 days old. You can find the certificate on the website of the Austrian Embassy in London."[1] There is however no mention of if the certificate can be in a digital form or has to be in the original paper form. If, depending on your situation, you are unable to receive the required certificate from your GP, you can get tested at the at the Vienna Airport on arrival (albeit for 190β¬). If you want to take this route, you have to make an appointment beforehand. More information can be found here.[2] austria.info also states the same requirements and was last updates on the 22nd of July. [3]
The official website of the Austrian Embassy in London also mentions the PCR/Swab Test but doesn't mention if a scan/photo of the form signed by your GP.[4] However, I would advise you to either take the original form, since there is no room for error, or take the test when you arrive at Vienna Airport or you also have the ability to take a test during your quarantine (in the case of a negative result you can finish your quarantine then and there).[1]
Sources:
[1] https://www.gov.uk/foreign-travel-advice/austria/entry-requirements
[2] https://www.viennaairport.com/pcrtest
[3] https://www.austria.info/en/service-and-facts/coronavirus-information