We had similar idiotic regulations in Holland. Most people rented their phone though they did have a plug (albeit a special one we called the pigs nose).
But in the 80s nobody gave a crap anymore and we just connected whatever we wanted. Aftermarket and technically illegal phones were sold everywhere.
Commodore made all kinds of wacky stuff back in the day before they concentrated entirely on computers and peripherals. I have a Commodore AM radio and a couple of Commodore wristwatches, chickenhead logos and all, not to mention the calculators and typewriters which were their original bread and butter.