Did you also tried WiFI without having Ethernet cable connected. As you can see in that Note from me, even after I add new default route I can’t ssh into device. Nor even ping gateway. Ping 8.8.8.8 work however apt-get update not, but resolve works. Quite weird stuff.
PS: To download over 380MB for network-manager on Server and then use it’s cli is not an option here, sure for tests but otherwise an no go.