Mac mini 2018 /iPad air 3 compatibility of Elgato video capture

I said nothing, nor implied anything about the integrity of El Gato. That is for your assessment alone. This is not an Apple issue, but one about the suitability of El Gato products for videotape to digital conversion. There may be other products, based on a search, that may be more suitable for this purpose, and I don't have videotape conversion history.

Have you contacted El Gato and requested their help in determining if this is possible?