Comment 5 for bug 1774120

The problem is that on WSL, it appears creating a raw socket is failing:

                sockfd = socket(AF_INET, SOCK_RAW, PF_INET);
                if (sockfd < 0) {
                        ebt_print_error("Problem getting a socket, "
                                        "you probably don't have the right "
                                        "permissions");
                        ret = -1;

That failure isn't going to happen on any 'actual' Linux system (baremetal, vm, or container) - unless you don't have permissions, as the error says. When upgrading a package using apt/dpkg on 'actual' Linux, you will have root access, and so will have permission to create a raw socket. So this is strictly a WSL problem.

Also, this is not a regression - the ebtables init script has behaved this way since trusty (and before). Since the ebtables project is essentially dead upstream, the package is very rarely updated and so WSL users simply haven't noticed this before because they haven't upgraded ebtables before.

However, as it's a trivial fix to the ebtables init script, and presumably a difficult fix to WSL, please test with the package from this ppa:
https://launchpad.net/~ddstreet/+archive/ubuntu/lp1774120

I think that should fix the problem for you - it will still print out a failure/warning message, but it should not break apt package upgrade. Note that I can't test this myself since I have no access to WSL.