Bypassing the switches is our next step here. Even with them reset to factory setting the switches can be doing something strange with multicast traffic.
Please temporarily move the PC + ID41 closer to the router and plug them both in directly, until you perform this test it is very difficult to say what exactly is going wrong or if the switches are playing a factor.
What does USB have to do with streaming over the network? These are two different protocols, just because USB works does not mean that the network input is free of configuration errors.
Firewalls have also often caused issues with Roon communication. Does turning off the firewall allow you to use your ID41 properly?