Small update: I have an USB 3 Ethernet adapter that also is a USB 3 hub and when plugged in directly, it actually works, yet the Ethernet port only works for a while. When in active use (transferring lots of data) it will suddenly stop working out of the blue. The system will show it being connected and working (green light in network preference pane) but in fact no data is ever sent out via that port if you try (I cannot even ping the router and switch confirms that no data arrives at all at the switch). Only unplugging and replugging the adapter will make it work again and this has to be done every 15 to 30 minutes on average. In between it works like a charm. Again, same adapter works on PCs and Intel Mac running Big Sur without any issues. So even when USB 3 is working, it is not working correctly or stable.

Since when? You can create your own SecAccessRef with multiple SecTrustedApplicationRef's created with SecTrustedApplicationCreateFromPath(). All of this is deprecated but it all used to work very well (we've used that many times in the past to work around access issues) and I just created a keychain entry that way in Swift 5 for a SecKeyRef and apparently it still works that way, as Keychain Access now lists all the apps I provided under Access Control in the list.