What is the problem with modern attempts to reincarnate push-button phones? They are all on Android, with a bunch of security holes. There are entire Chinese series that steal money and user data and brazenly send SMS secretly.
Those who are really smart and want to have a push-button phone for reliable dual authorization via SMS on the main smartphone (only morons accept dual authorization SMS on the same phone where there is access to online banking and the login and password have already been entered) are looking for old models of push-button phones released before 2010-2011. They are reliable and not on Android. They do not have malicious Trojans in the firmware, especially from well-known brands.
Now you can organize a new profitable business simply by selling old push-button branded phones - they are very popular with adequate people and therefore in huge shortage. Now many are biting their lips, who threw away the old push-button phone.
Although in some countries GSM/2G/3G networks have already been switched off, so, unfortunately, the good old and reliable push-button models will no longer work there....