While in Mailman Settings a user can change delivery mode for either Global (all subscriptions regardless of address or list), Address based (regardless of list name) or List Based (regardless of address).
The list admin can change a user's delivery mode setting on a single list (affecting only that address and only that list), but only one subscriber at the time on the list.
Changing a user's delivery mode can also be done using REST[1], but I asume this will affect the user's subscription on all the lists where she subscribed using the same address.
How do I change ALL the subscribers[2] on a _single list_ to a certain delivery mode, using REST?
[1] https://mailman.readthedocs.io/en/latest/src/mailman/rest/docs/preferences.h... [2] Most likely by iterating through all subscribers, one at the time, on the list in question.