@Swede1952 @ety @x00001 I'm serious...
In fact such "#FWT" or "Fixed Wireless Terminal" adaptors are actually quite common, as they basically allow folks to keep their beloved phones - espechally those with hearing aid compatibility or additional functions like a wireless emergency button - and just transition from (sadly discontinued and) expensive "basic landline" to cheap pay-as-you postpaid or prepaid plans.
- In some cases they even allow people to port their landline number to some providers, so that i.e. seniors can retain their decades-old number and in return get like good reception because most FWTs come with an option to plug in an external antenna...
OFC those boxes exist in various forms, from something akin to a Router like the Fritz!Box LTE series to the more commonplace "Trashcan"-esque cylinders for #5G-#MIMO. Sadly most don't include like a batter backup but there are also "#GSM #DeskPhone|s" that are basically #StupidPhones (some absurdly expensive ones are just bulky #smartphones, #Phablets if not #Tablets) with dedicaded physical buttons and aside from being able to send/recieve #SMS and potentially offer a #WiFi hotspot as well as almost always have a prominently large antenna sticking out the back, they look like your average Desktop Phone from an office...