I have always used a Tee connector with the signal generator and the signal detector connected to the straight through connections, and the stub connected to the 90 degree angled connector. Just about any combination of signal generator and signal detector could be used, certainly including a NanoVNA. I have Tees here in several connector styles, including SMA, BNC, UHF, and probably others. I used to sweep stub filters with a Cushman communications monitor with spectrum analyzer and tracking generator, which had all BNC connectors as I recall. But I still used it for making RG-59 stubs with F connectors by using a BNC to F adapter on the stub. So long as the adapter is short and an insignificant portion of a wavelength at the desired frequency, it won't affect the measurement. I have also soldered cables together to make the Tee and stub and avoid the adapters.
Jim Allyn - N7JA