If i choose to have "less" security by using email (in fact its more, but thats a different topic) it should be my choice. I should not be forced to own a fixed telephone number, especially for services that just dont know any better. I should also not be forced to give away possible access to my accounts just because i tend to change phone numbers.

Edit:// To your edit. With "nomad" i dont mean i live like a outcast. I am currently living as digitalnomad. I have a home address and earn money, i just dont have a fixed telephone number anymore.

Anyway there are mail providers who won't ask you for a mail. Protonmail and GMX come to my mind.

If they require telephone number i would at least expect them to support a wide range of providers and not only some. Like i really cant get over the fact that Twitter locks out the most popular Thai provider.

They however could also send me a letter, or have me auth with Authy/Google Auth to make a single identity system. Maybe even requiring my passport number + name. Its not like phone would be the only solution.

And yeah i see that may is hard for small providers, but it shouldnt be hard for bigger ones. Or like in Twitters case, its not about having a single account anyway, you can have hundreds with the same phone number, but not a single with a thai phone carrier.

Edit:// To clearify i personally have no issue with initial confirmation over SMS, i mean i own a phone number most of the time. I just not own it for longer than a month, so it is not valid for me for further authentication.

You can create throwaway SMS numbers for a few cents with several online providers, some even accept Bitcoin payments and dont ask for a name and Twitter accepts them happily. Its just the third party provider they use that did not implement that specific carrier yet.

Edit:// Also i am curious now why you think i had a thai phone number while living in switzerland? :D There are countries like austria that dont even ask for a passport for prepaid directly next to it, why would i go thai?

At least here it's not legal for a mobile operator to give you a phone number if they don't have your ID (not even a prepaid number) so I supposed it was the same in the whole EU. Therefore I imagined you heard somewhere there's an operator in Thailand that lets you get a number without giving an ID, maybe even for free, so you wanted to get one to auth in Twitter. But such a system would be abused by spammers so Twitter had blocked that operator already.

Yes, quite the elucubration, I know.

Having important services tied to a phone number, which remains relatively tied to a country is problematic in the modern world even for people who aren't especially "outcast".

So very much a partial solution. In particular, it's no good for someone who moves long-term or, say, someone studying in another country. Simply changing phone numbers with a bunch of services is a serious pain in the ass even if they all consider the new number acceptable.

As an American currently living in Germany, I've run in to this kind of problem myself. My mobile banking app, for example wants to send an SMS for verification because it thinks connecting from an non-US IP address is suspicious, but I can't give it a non-US phone number to do that with. Providing a different option for 2FA would be a big help.