As a newcomer to Linux and Linux-based virtualisation, your time might be better spent putting this network card issue aside for a while and sticking with PVE8. I have a similar network card in my setup, so was interested in your report. It's a common card so should surface again soon as more users upgrade and experienced users take an interest in it. But if it is associated with a specific and old hardware combination (motherboard?) you may be out of luck. I have winged it for a long time on old hardware but PVE9 may present some issues for me! I may be OK in this instance as I have not enables passthrough and your problem looks to be connected to IOMMU.
I have not come across another community forum where you'll find the same level engagement as you do from the staff here. This forum is an amazing resource. My only problem is using google these days to find the posts that help me.
I didn't specifically enable passthrough, and I'm just a baby newcomer to Linux, so I don't know if passthrough is something that happens during install or not. Yet

Don't feel alone in regard to google. It works, of course, but takes a lot of sifting. I've been using Grok and GPT-4 for searches, which returns source and synopsis.