BlackMagic Intensity Shuttle - No Desktop Video Device Detected - Apple Mac M1
According to https://www.blackmagicdesign.com/support/readme/33abc1034cd54cf99101f9acd2edd93d Intensity Shuttle doesn't seem to be supported on M1 currently:
Intel Macs only:
...
Intensity Shuttle Thunderbolt
So you have to wait for the vendor to add support for M1.