In The Netherlands I wouldn't be able to login to any government or adjecent websites (e.g. portal of my local health center/GP, health insurance, retirement/pension insurance) without a smart phone running DigiD app for 2FA.
The non-EU Serbia has the equivalent app, but also you might be able to get individual/personal e-certificate (for logging into e-government or signing e-documents) added into smart card chip of your ID. But in practice it seems thats only used for business purposes, like CEO/Accountants/etc to sign/submit business records/taxes.
In Belgium the eID software runs on GNU/Linux, so I can log in to government websites using my ID card and a card reader. In my experience it even works better on GNU/Linux than on MS Windows.
It's one of the only things that Belgium does right.
The DigiD app isn't required. You can log-in with DigiD using SMS 2FA. This is what I currently do, because I don't want to install closed-source software on my device.
I used to work for a GSM messaging gateway/SMSC. And seeing first hand how most of those SMS messages (2FA, password reset, bank transaction/balance ...etc) are usually routed (sure over SSL but stored/forwarded as unencrypted GSM packets) through several different companies around the world - before reaching your mobile operator ...
And on top of that you add stuff like sim cloning, and all the other things that one gets by having a direct SS7 connection (there were blog posts/YouTube videos - IIRC Linus Tech Tips calls/SMS got routed to Australia).
Using SMS for 2FA or anything similar is my last resort.
Granted I stopped working there 15+ years ago - but I imagine that the basic economy reasoning where it's impractical for every mobile operator to have a direct peering contract with every other operator in the world - is still the same.
And messages originating from non mobile users/operators (like DigiD 2FA) always start at one of these messaging gateways/SMSCs (e.g. InfoBip.com), and often go through a few different ones before reaching your mobile operator.
The non-EU Serbia has the equivalent app, but also you might be able to get individual/personal e-certificate (for logging into e-government or signing e-documents) added into smart card chip of your ID. But in practice it seems thats only used for business purposes, like CEO/Accountants/etc to sign/submit business records/taxes.