If you'd like to stop receiving push notifications for Chat, here are several options:
Turn off notifications for a specific thread
Tap on a thread and select the toggle next to "Reply notifications".
A gray toggle means that notifications for that thread have been turned off and you won't receive any push notifications.
Note: At this time, you can only turn off notifications for specific threads and not mute the entire Substack's Chat.
Turn off all notifications for Chat
Tap your Profile icon and select the Settings gear in the top-right corner. Tap "Notifications" and on this screen, make sure that the toggles are on the left for each item listed in the Chat section. You will not receive any push notifications about Chat.
To leave a Chat
At this time, the only way to fully leave a Chat is by unsubscribing from the publication.
On the publication's page, tap the three dots in the upper-right corner. Select "Unsubscribe".
Tip: Once you unsubscribe from a publication, it will not appear in your Library or your Chat.