I have a laptop plugged into a device with what I believe is a link-local IPv6 address via an ethernet cable. The laptop is connected to a VPN I have created. I am connected to the same VPN on another laptop and can ping back and forth. I can ping the device from the laptop connected to it via cable but not from my remote laptop.
The device can only do IPv6 not IPv4.
I think I can make a managed route in Zerotier but unsure how to do this with IPv6. Does anyone have any ideas?
Link-local addresses are not routable. Given that every device with IPv6 already has an interface in fe80::/64, you would never get there even if your router would route it.
You want a ULA instead, and to create route to that in Zerotier.