> No idea why self-hosted software isn't `apt-get install` and forget.
Some of it is. But as soon as you want your services to be accessible from the Internet, you need to have a domain name and HTTPS. To run Limewire or a BitTorrent client, you don't need a domain name yourself because you use a central server (in the case of BitTorrent, a tracker) to help you discover peers.
All the popular domain name services and certificate issuers have APIs. All grandpa has to do is go online and buy a domain - which is a very reasonable step that grandpa can do. Grandpa, after all buys stuff online. But after that the self-hosted app should be able to leverage the APIs to configure all the settings.