[server] 15.10 - Tried updating/installing dependencies and now broken

Does it offer an option to continue to boot despite that error? Also, I really recommend coecting it to your home LAN so that it can have inteet. How will you be doing updates?

And you chose the 15.10 which is non-LTS and has only 9 months of support. The general idea is always to use only LTS versions for servers, even for home servers. You went through all the problems to set it up and configure it, and in few months it will be out of support.

For servers don't install the latest non-LTS version automatically, unless it's only for testing something. Always use the LTS versions.