Looks as if my Internet works at home—after a false start.
HanseNet/Alice had "hijacked" my connection to display a setup web page no matter which URL I entered. I had kind of suspected that and was ready for it.
However, it wouldn't let me configure my account: step 2 was to set up an email address, either by accepting the one they chose for me or by entering one of my own. However, regardless of which option I picked, I didn't go to step 3 but instead to a generic search page in their customer account site. Trying to pick any account option required me to log in again, at which point I was back to step 2 of account setup.
So I called the hotline and chose option 6 for technical support. I was advised that this would cost €5.99 per call, but what was I to do? So I accepted. I was told that the wait would be "more than five minutes", and got to listen to hold music punctuated occasionally with a request to "please wait for just a moment and we'll put you through to a CSR". The "just a moment" ended up being 21 minutes (during which I played some Solo to keep myself sane).
The rep said he'd try to set up the account for me but warned me beforehand that he might end up getting trapped in the loop as well. (That didn't bode too well.) However, it apparently worked for him, until he got to the last step, which told him that "your request could not be carried out at this time; please try again later". However, he said that the email account did appear to have been set up correctly, so he advised me to ignore that message.
He asked me to disconnect from the Internet and reconnect; when I did and restarted my browser, it showed my configured home page rather than one of their pages, and things seem to be working now.
Still, a slightly annoying start to things.
Oh, and I'm not using the WLAN DSL router thingy they sent me. Instead, I'm using the hardware I used with my last DSL provider, merely using a different login, and that works well enough. So Stella can't use the Internet from her laptop, but if things go the way they appear to be, we won't be in this place for that much longer anyway. (And besides, the WLAN adapter in this computer is supposedly capable only of 2 Mbps, so I wouldn't be able to use all 4 Mbps of our new DSL connection, so I'd probably want to hook up my PC using cable anyway—in this case, presumably Ethernet cable to the DSL router rather than DSL cable to the DSL card in my PC the way things are now.)