This is the form website https://entry.ptc.gv.at/en.html
Press "One or more of the exceptions mentioned in § 7(1) or § 8 of the COVID-19 entry regulation are applicable to my entry." and it'll say you're exempt. Furthermore, the site then won't even let you press the button to submit (it also requires an Austrian address, which is obviously not ...
According to the Pre-Travel Clearance website of the Austrian government, you are exempt from filling out the form.
In accordance with Section 7 para. 1 and Section 8 of the
COVID-19-Einreiseverordnung registration with the pre-travel clearance
form is not required: […]
When entry is related to other exceptions in accordance with Section 8
para. 1 and ...