Game server can connect on WiFi but not ethernet
I postulate a couple of possibilities -
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Your devices are all on WIFI, and the router is set to do LAN ISOLATION - ie firewalling off WIFI from the LAN and is a fairly common security setting.
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The Paper Minecraft server is binding on a specific IP/interface - the one associated with the WIFI connection. (https://www.minecraftforum.net/forums/support/server-support-and/2963730-failed-to-bind-to-port might be useful?)