What knc1 said. On a vanilla device, you shouldn't have been able to connect over WiFi. USBNet doesn't touch that by default.
There's a dedicated setting in USBNet that makes a hole in iptables for SSH over WiFi [and only that] (aptly title 'Enable SSH over WiFI' in the KUAL extension) , but if you want more control over the whole rule set, follow knc1's advice, it's his baby
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