Cannot Ping Subnet Devices Connected to Odroid M1

I have close to zero computing knowledge but was able to set up and be able to ping subnet devices behind a RPi running Tailscale 1.26.1, following the instructions in Subnet routers and traffic relay nodes · Tailscale. Unfortunately I can’t do the same with an Odroid M1. IP forwarding is correctly enabled I think, but the final command “firewall-cmd --permanent --add-masquerade” is not accepted. Does anyone know what the correct procedure is for setting up the Odroid M1 with subnet routes? The Odroid is running Hardkernel’s version of Ubuntu 20.04 LTS and Kernel 4.19.219. Thank you.

Off-hand I don’t remember what the error might be that you would be seeing. Do you get an error output from firewall-cmd --permanent --add-masquerade? If so would you mind sharing the error?

Thank you Raggi. In response to “sudo firewall-cmd --permanent --add-masquerade” it responds “firewall-cmd: command not found”. I looked around to see if Odroid/Hardkernel’s version of Ubuntu required a different command but was not able to find it. Any help gratefully received.