As far as I can see, a single udhcpd will only serve one network interface at a time, so you'll need to run a second copy of it with a separate configuration file whenever you want it to serve DHCP on eth0 too. That might be called /etc/udhcpd-eth0.conf.
You might also need two copies of /etc/network/interfaces at a separate location, one with the "DHCP ...
Using OpenSSH in Linux, tunnels can be created over SSH using either TUN or TAP interfaces, as long as proper routing is setup and ip forwarding where appropriate.
For creating a TUN tunnel, will leave here a practical script, from Ip Tunnel Over Ssh With Tun ; the script assumes you are running as root.
Add “PermitTunnel yes” to /etc/ssh/sshd_config
Assuming you are allowed to assign yourself an IP, and I don't know if you've been doing this correctly, your netmask:
In combination with your working IP:
Leaves you with this subnet: 192.168.0.0/24, which means you in no way could assign yourself any IP starting 192.168.10.. You could only change the last number in 192....
As my comment implied, you can't bond such connections.
Bonding is a layer 2 concept, ideally invisible to the higher layers. This means that packets addressed to your IP may appear at both interfaces, scheduled by the device sending the frames to you.
However, with your connection to the ISP you have two different L3 devices, which have different IP's ...
command2 is not "dangling", it is a post-up option for eth0, so it will be executed right after command1. From man interfaces:
Options are usually indented for clarity (as in the example above) but are not required to be.
Also, empty lines are ignored in /etc/network/interfaces (and in all included files).
Debian also has a package for ConnMan, which is not affected by the issue you mention for NetworkManager. You might benefit from checking the common problems "Tips and Tricks" section on the Arch Wiki page, however.
On systems unlike yours, where policykit-1 is available, the upstream ConnMan can use it to selectively grant access to unprivileged users. ...
Before network-manager, the well-known way to "automatically ifup the network interface when a cable is plugged in" was ifplugd. (Note the original author :-P). ifplugd is still available in Debian. I do not have any recent experience with it.
Firstly, you would remove the auto eth0 or allow hotplug eth0 line from /etc/network/interfaces. You would ...