I don’t have a solution for you, but a suggestion as to a path to investigate. The fact there is no outgoing traffic suggests a local config issue. I’m assuming the remote wireguard server is NOT a GL-MT300N-V2.

My suggestion is you create a wireguard SERVER config on your GL-MT300N-V2 and print that out. On the assumption that gl-inet tested their own sever with their own client , presumably this would work if imported . The question this is how does it differ from the one you are using.

e.g. I note my exported config (for the client to use) has:

Address = 10.0.0.1/32 (not just 10.0.0.1)

Might just be a local parsing error