I plugged into ethernet (as wifi w/captive portal does not work for me). I think clearnet worked but I have no interest in that. Egress Tor traffic was blocked and so was VPN. I’m not interested in editing all my scripts and configs to use clearnet, so the library’s internet is useless to me (unless I bother to try a tor bridge).
I was packing my laptop and a librarian spotted me unplugging my ethernet cable and approached me with big wide open eyes and pannicked angry voice (as if to be addressing a child that did something naughty), and said “you can’t do that!”
I have a lot of reasons for favoring ethernet, like not carrying a mobile phone that can facilitate the SMS verify that the library’s captive portal imposes, not to mention I’m not eager to share my mobile number willy nilly. The reason I actually gave her was that that I run a free software based system and the wifi drivers or firmware are proprietary so my wifi card doesn’t work¹. She was also worried that I was stealing an ethernet cable and I had to explain that I carry an ethernet cable with me, which she struggled to believe for a moment. When I said it didn’t work, she was like “good, I’m not surprised”, or something like that.
¹ In reality, I have whatever proprietary garbage my wifi NIC needs, but have a principled objection to a service financed by public money forcing people to install and execute proprietary non-free software on their own hardware. But there’s little hope for getting through to a librarian in the situation at hand, whereby I might as well have been caught disassembling their PCs.
The reality despite what you or i might do, is that 99% of people don't carry around an ethernet or hardwire in when there is available wifi.
The library might be public, but it's still a good idea to communicate your intent or obtain permission prior to using someone else's network in away they might deem to be unexpected.
"Do you have ethernet or wired internet?" is actually a common library question and the response from whoever works the front desk will likely tell you everything you need to know.
Would you trust the reply somebody like the librarian in the OP gave you? Seems like the sort of person who would refuse to admit to any lack of knowledge and just bluster.
As far as people I’d trust to not just make shit up, I’d say Librarian, aka, professional fucking researcher is high on the list.
That pretty much depends on where in the world you are, FYI. Librarian == professional fucking researcher is not a thing in Asia.