Share… on a list adds people or channels, each at Can view or Can edit; a new share starts at Can view. Somebody it is shared with who is not in its channel opens that list at its usual address and nothing else of the channel, and is told in Activity and on their phone who shared it. An item assigned to them there reaches them too.
Every list has an owner — whoever made it, until they hand it on with Transfer ownership. The owner, or whoever manages the channel, can make the list view-only for the channel’s members, and the server then refuses every change from somebody who may only view it. Duplicate list copies its fields and views, with its items or without, and none of its shares.