I mean: I could leave it there, right? We all know they do. I use them as a puzzle: what e-mail address and phone number will pass their validation criteria? Sometimes it's a@b.com that's good enough, but it's the phone numbers that can be a real challenge, though it's helpful if there's a nearby advertisement you can read one off.
As might be obvious from this topic, I'm travelling at the moment - partly to attend DebConf26, and partly because meeting new parts of the world (and the people who live there) can be very enjoyable. Some people would class me as a frequent traveller, and I do have a bookmark for 'http://neverssl.com' which can be very helpful with most captive portals.
Not this time though, and I spent way too long before twigging that hotel WiFi was in the same IP range as my fourth Docker network. As a long-term Docker user for some reason(s) I have managed to be operating networks on 172.17/16, 172.18/16, 172.19/16, 172.20/16, 172.21/16 and 172.22/16!
Goodness! What a lot of networks! I guess at various times over the last 20-odd years of using this laptop (same laptop: 14 different storage devices, 6 different hardware platforms) I've installed different docker compose setups, k3s, and so forth, and with each increment, the odds of getting bitten by a hotel running their captive portal on one of these increases a bit, so it was bound to happen eventually.
Ah well: I guess being forcibly overnighted in an airport hotel is a good opportunity to clean it all up!