If the protocol doesn’t support it, then the sorting can’t be communicated to other clients. That means everyone has to individually do the work to sort them.
The protocol can be edited by clients, for example I believe FluffyChat and Commet both support user profiles, even though its not an official part of the spec yet.
Matrix doesn’t support sorting channels into a defined order.
Element doesnt, but theres a lot of other clients that might.
If the protocol doesn’t support it, then the sorting can’t be communicated to other clients. That means everyone has to individually do the work to sort them.
The protocol can be edited by clients, for example I believe FluffyChat and Commet both support user profiles, even though its not an official part of the spec yet.