You can try the latest release of BlynkEthernet_WM Library which provides Blynk support to Teensy 4.1 using NativeEthernet.
Try this NativeEthernet_WM_Config_Teensy example to see if OK for you.
This library is based on EthernetWebServer Library, which has been tested with Teensy 4.1 NativeEthernet.
Be sure to update the Teensy core to latest v1.53, and install related libraries to compile and run.
Good Luck,