My previous setup that worked on Intel with Sonoma was the DeckLink 4K mini monitor and for me I was using the Razor box. I am assuming we’re talking about the same thing.

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If so, it has not worked for me on Mac Mini M2 Pro running Sequoia. I was using Display Video 14.9. It could be MacOS Sequoia, or DV 14.9. But I stopped fooling around with it and used the UltraStudio mini monitor 3G which worked.
Now, back on the Intel Mac, when I installed Sequoia and DV 14.9, I couldn’t get it to work. I swapped the Razor/DeckLink 4K card with an UltraStudio mini monitor HD and that too didn’t work. I researched and f around it trying to get it to work and I found a post recommending to downgrade to DV 12.5. That finally worked (see discussion here):
viewtopic.php?f=3&t=221671&p=1157875#p1157875So you can try going back to Sonoma - that might take care of the issue. Another is to try a version of DV, either 12.5 on Sequoia or 14.9 on Sonoma like what Uli said works for him. If those won’t fix it, I say it’s likely the external PCIe chassis that’s not known or supported by the OS. Good luck.
EDIT: I never tried using the UltraStudio mini monitor HD on the Mac M2 Pro so I couldn’t tell you if that option works. I’m curious if you don’t need 4K monitoring and the OS is Sequoia and DV is version 12.5 will it work? You can buy those UltraStudio mini monitor HDs on eBay for $20 or less last I saw.
URSA Mini Pro 4.6K G2, BMPCC 6K. iMac Pro 27” 5K Retina, 64gb, 1Tb SSD, 12Tb M.2 NVMe TB4 DAS, 36Tb HDD DAS, Vega 56 8gb GPU/ BM Vega 56 8gb eGPU, MacOS Sequoia+DVRS 19.1.4, BM Panel & Speed Editor. Mac Mini M2 Pro 10/16 cores, Sequoia+DVRS 20