The short answer is “I don’t know” unfortunately but curious what your use case is? Are you trying to hook up multiple DX I/O’s to the Avantis SLink port? If so, why not use DX HUB (is it a cost issue) or daisy chain (on the 16 port IO’s)?
Seems to me that the DX HUB is essentially a 5 port ethernet switch with 1 port working at 1GB (GigaACE) and 4 ports working at 100MB (DX/dSnake) (but I could be way off base here). In the old days you could probably find 100MB switches with a 1GB uplink but not seeing them widely available with how inexpensive 1GB has become.
You might try a 5-port 1GB L2 managed switch. Turn off every possible enhanced feature in the switch (so it’s as dumb as possible), hard code 4 of the ports to 100MB FDX, one port to 1000GB, and experiment. Avantis, connected at 100MB should support 32 total channels (DX) whereas it should support 128 total channels when connected at 1GB (GigaACE).
If you can though, do what you are trying to do through a supported existing mechanism (either the daisy chain port or DX Hub) to minimize potential issues and support finger pointing.
Some background info I found
https://support.allen-heath.com/hc/en-gb/articles/4403666880913-General-Connecting-to-the-SLink-port-
https://support.allen-heath.com/hc/en-gb/articles/4403304180497-Audio-Networking-Can-I-run-dSNAKE-through-a-network-switch-
https://www.allen-heath.com/media/DX-GX-System-Guide-ISS_5.pdf
Network switch on the Slink to protect
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