I just want to share a working config in case anyone is facing a move to a Thunderbolt 4 equipped, non-PCIe, Mac.  The Thunderbolt 2 to 3 adapter for apple works with my T2 Sonnet chassis. 

I had been using the original AIO card with AIS and AOS daughter cards for years in a Mac Pro.  I only needed one actual slot but the one slot chassis don't have room for two daughter cards and I didn't want to spend the extra (usually double) money for a two slot chassis - I lucked out and found a used older gen chassis for a good price.

I was a bit unsure that an older Sonnet chassis would work or that it would work with an adapter.  Happy to report that it does.  You can also upgrade the older chassis to T3 with a card but its currently a $200 part vs a $40 adapter.