i think phones are a better analogy to fedi than email because with email everyone uses more or less the same stuff, but with phones (and fedi), you might be calling from your brand new and shiny iphone 15 pro, but on the other side there might be alexander graham bell saying "HULLO?? HULLO????" into his elaborate and goofy copper wire tele-phone
@halva during the start of the Covid pandemic the Queen (who was still alive then) had a phone call with the Prime Minister, she used an old style 8746 telephone - these stopped being common in the early 1990s) (although it would have been connected via an analogue telephone adapter to a heavily encrypted VOIP circuit)