I wonder if there is a way to disable this SMS 'security' antifeature once and for all? I imagine it is a constant nightmare for people who travel abroad and do not always have connection on their number registered in their 'home' country.

Indeed. I have a university alumni account that I haven't been able to use for some years because it is managed by Google, and they in their wisdom figured somethings was suspicious (maybe leaving the country or not logging in multiple times a day or cleaning cookies or something else that good patriots don't do).

They're asking for a phone number (so, good to know - if a hacker actually got my username and password, they could access everything Google has on me if they have a fresh phone number, I feel super protected), which I am reluctant to provide, but it still doesn't work.

As you highlight, no support.

On Gmail: https://myaccount.google.com/security -> "How you sign in to Google" -> "2-Step Verification Phone" -> trash can.

In general, no. I've wondered if legislation would be feasible though, especially given the flaws that have already been shown.

To be a person is to have a phone number capable of receiving SMS, at least according to approximately every US company.